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A2 noun #8,000 most common 10 min read

弟さん

otoutosan Top 8,000

Practice it Examples Notes & Tips 弟さん in 30 Seconds

Explanation 弟さん in your Level:

At the A1 level, you are learning the basic building blocks of family vocabulary. 'Otouto-san' is introduced early because talking about family is a fundamental part of introductions. You will learn that 'otouto' means younger brother and that adding '-san' makes it polite. The focus here is simply recognizing the word and understanding that it refers to someone else's brother, not your own. You will use it in very simple sentence structures like '[Name]-san no otouto-san desu' (It is [Name]-san's younger brother). You don't need to worry about complex honorifics yet; just focus on the distinction between 'otouto' (me) and 'otouto-san' (you/them).

At the A2 level, you begin to use 'otouto-san' in more interactive contexts. You will learn to ask questions about other people's siblings, such as their age, their hobbies, or where they live. You will also start to understand the particle 'no' for possession more deeply. At this stage, you should be comfortable using 'otouto-san' in standard polite (desu/masu) conversations. You are learning to navigate basic social interactions in Japan, and correctly identifying family members is a key part of that. You will also start to see the kanji 弟 more frequently and should be able to recognize it.

At the B1 level, you are moving beyond simple questions and starting to describe relationships and situations involving younger brothers. You might talk about how someone's 'otouto-san' resembles their father, or discuss their career paths. You will also become more aware of the 'Uchi-Soto' (Inner-Outer) social concept, which dictates why 'otouto-san' is used with outsiders. Your vocabulary is expanding to include related terms like 'gitei' (brother-in-law) or 'sue-ko' (youngest child), and you can compare these to 'otouto-san'. You can handle longer conversations where 'otouto-san' is the topic of a story.

At the B2 level, you should have a firm grasp of the social nuances of 'otouto-san'. You understand that even among close friends, using 'otouto-san' can still be appropriate to show respect for their family. You are also learning about different registers, such as when to use 'otouto-kun' for a more casual, friendly tone when talking about a younger boy. You can understand more complex grammar involving 'otouto-san', such as honorific verbs like 'irassharu' (to be/to come) used in conjunction with family members of others. You can discuss social issues like birth order and its impact on Japanese society using this term.

At the C1 level, you are exploring the literary and highly formal uses of the term. You will encounter variations like 'gotei-kun' in formal correspondence or literature. You understand the historical development of the kanji 弟 and its philosophical implications in Confucian-influenced Japanese society. You can navigate high-level business or formal social events where the choice between 'otouto-san', 'otouto-sama', and 'gotei' carries significant weight in terms of etiquette and social positioning. You are also sensitive to the regional variations or more archaic terms that might appear in classical literature.

At the C2 level, your understanding of 'otouto-san' is near-native. You can appreciate the subtle irony or sarcasm that might be intended if someone uses 'otouto-san' for their own brother (breaking the humility rule for effect). You can analyze the use of the term in various historical periods and its role in defining the 'ie' (family) system in Japan. You are capable of translating complex English texts about family dynamics into Japanese, choosing the precise level of honorific for 'younger brother' that matches the source text's tone and context perfectly. You understand the deepest sociolinguistic layers of the word.

Practice it Examples Notes & Tips

弟さん in 30 Seconds

Used for someone else's younger brother.
Combines 'otouto' (younger brother) and '-san' (polite suffix).
Essential for polite social interaction in Japanese culture.
Never used for one's own brother in front of outsiders.

The Japanese word 弟さん (otouto-san) is a polite noun used specifically to refer to someone else's younger brother. In the complex world of Japanese social dynamics, the language distinguishes sharply between one's own family members (inner group or 'uchi') and the family members of others (outer group or 'soto'). When you are speaking to a friend, a colleague, or a stranger about their younger brother, you must use this honorific form to show proper respect and social distance. The word is composed of the kanji 弟, meaning 'younger brother', and the ubiquitous honorific suffix さん.

Social Hierarchy: In Japanese culture, hierarchy is not just about age but about group affiliation. Using 'otouto-san' elevates the status of the listener's family, acknowledging that they are outside your immediate circle and deserve a higher level of linguistic politeness.

田中さんの弟さんは、大学生ですか？ (Is Mr. Tanaka's younger brother a university student?)

The kanji itself, 弟, has a fascinating history. It is said to depict leather straps or string being wound around a central pole or piece of wood. This imagery originally represented the idea of 'order' or 'sequence,' specifically the sequence of birth. Just as the string follows the pole, the younger brother follows the elder brother. Over time, this evolved to specifically mean the younger male sibling. When you add 'san', you are essentially saying 'The Honorable Younger Brother'.

Kanji Breakdown: The radical is 弓 (bow), though its modern form looks more like a series of strokes. It is often taught alongside 兄 (older brother) to establish the family vocabulary foundation.

佐藤さんの弟さんによろしくお伝えください。 (Please give my regards to Mr. Sato's younger brother.)

You will encounter this word in almost every social setting where family is discussed. Whether you are asking a classmate about their siblings or inquiring about a business partner's family during a polite dinner, 'otouto-san' is the standard, safe, and correct choice for a younger brother who is not your own. It bridges the gap between casual friendliness and formal respect.

あそこにいるのは、あなたの弟さんですか？ (Is that person over there your younger brother?)

Register Variation: While 'otouto-san' is neutral-polite, in very formal situations, you might hear 'otouto-sama', and in very casual situations among friends talking about a younger boy, 'otouto-kun' might be used.

昨日、デパートで鈴木さんの弟さんに会いましたよ。 (I saw Mr. Suzuki's younger brother at the department store yesterday.)

弟さんは何人いらっしゃいますか？ (How many younger brothers do you have? - using very polite language.)

Using 弟さん (otouto-san) correctly involves understanding the particles that connect it to the rest of the sentence. Because it is a noun referring to a person, it often acts as the subject (marked by は or が) or the object (marked by を) of a sentence. It is also very common to see it preceded by a name and the possessive particle の (no).

The Possessive Pattern: [Name] + さん + の + 弟さん. Example: 木村さんの弟さん (Kimura-san's younger brother). This is the most common way to identify whose brother you are talking about.

木村さんの弟さんは、テニスが上手ですね。 (Mr. Kimura's younger brother is good at tennis, isn't he?)

When asking a question directly to someone about their brother, you can omit their name if the context is clear. For instance, if you are talking to your friend Ken, simply saying 'Otouto-san wa...' implies 'Your younger brother...'. This is because Japanese often omits the subject when it is understood.

Verbs of Existence: When asking if someone has a younger brother, use います (imasu). Example: 弟さんがいますか？ (Do you have a younger brother?)

山田さんには、弟さんが二人います。 (Mr. Yamada has two younger brothers.)

In more descriptive sentences, 'otouto-san' can be the recipient of an action. If you gave a gift to someone's brother, you would use the particle に (ni) to indicate the recipient. The level of politeness in the verb should match the respect shown by using 'otouto-san'.

あなたの弟さんに、この本を貸しました。 (I lent this book to your younger brother.)

Comparison with 'Otouto': If you say 'Watashi no otouto-san', you are essentially being 'too polite' to your own family, which sounds strange or even sarcastic in Japanese. Always stick to 'otouto' for your own.

小林さんの弟さんは、お父さんにそっくりですね。 (Mr. Kobayashi's younger brother looks just like his father, doesn't he?)

Finally, remember that 'otouto-san' is a complete noun. You don't need to add another 'san' after it. The 'san' is already baked into the word to provide the necessary politeness level for general conversation. It is a workhorse of Japanese social etiquette.

昨日のパーティーに、弟さんも来ましたか？ (Did your younger brother also come to yesterday's party?)

You will hear 弟さん (otouto-san) in a wide variety of everyday situations in Japan. It is not just a textbook word; it is the standard way to navigate social interactions involving families. One of the most common places is at the front door of a friend's house. If you are visiting a friend and their younger brother opens the door, or if you are asking the mother where the younger brother is, 'otouto-san' is the respectful term to use.

School and University: Students often talk about their families. If a senior (senpai) is talking to a junior (kouhai) about the junior's family, they will use 'otouto-san' to maintain a polite yet friendly distance.

「あ、健太君の弟さん、さっき公園にいたよ。」 (Oh, Kenta-kun's younger brother was at the park a moment ago.)

In the workplace, Japanese professionals often engage in 'small talk' (settai or zatsudan) to build rapport. Asking about a colleague's family is a common way to do this. Even if you are close with your colleague, using 'otouto-san' shows that you respect their family members as distinct individuals worthy of honorifics.

Service Industry: If you go to a family-run restaurant or a local shop where the staff knows your family, the shopkeeper might ask, 'Otouto-san wa ogenki desu ka?' (Is your younger brother doing well?). This builds a sense of community.

「弟さん、もう高校生になったんですね。早いですね！」 (Your younger brother is already a high school student, isn't he? Time flies!)

Anime and Drama fans will frequently hear this word. When a protagonist meets their rival's younger brother, or when a neighbor stops by to drop off some food, 'otouto-san' is the go-to term. It establishes the relationship immediately: the speaker is talking to or about someone else's sibling. Pay attention to the tone—it's usually warm and polite.

「あちらに座っているのが、私の親友の弟さんです。」 (The person sitting over there is my best friend's younger brother.)

Neighborhood Gossips: In local neighborhoods, people often track the milestones of the children living nearby. You might hear neighbors chatting: 'Tanaka-san no otouto-san, kekkon shita sou desu yo' (I heard Mr. Tanaka's younger brother got married).

「弟さんのお名前は何とおっしゃいますか？」 (What is your younger brother's name? - very polite.)

In summary, 'otouto-san' is ubiquitous because family is a central topic of conversation in Japan. It serves as a polite linguistic marker that respects the boundary between your family and others, making it an essential tool for smooth social navigation.

The most frequent mistake learners make with 弟さん (otouto-san) is using it to refer to their own younger brother when speaking to someone else. This is a significant cultural faux pas. In Japanese, when you talk about your own family to 'outsiders', you must use humble language. This means stripping away honorifics like 'san'.

The 'Uchi' Rule: Correct: 'Watashi no otouto wa gakusei desu.' (My younger brother is a student.)
Incorrect: 'Watashi no otouto-san wa gakusei desu.' (This sounds like you are giving your own brother unearned respect in front of others.)

❌ 私の弟さんはアメリカにいます。
✅ 私の弟はアメリカにいます。 (My younger brother is in America.)

Another mistake is confusing 弟 (otouto) with 妹 (imouto). While they look somewhat similar in their kanji (both have a 'vertical' feel), 'otouto' is for a younger male sibling, and 'imouto' is for a younger female sibling. Mixing these up can lead to confusion about the gender of the person you are discussing.

Over-politeness: Sometimes learners say 'Otouto-san-san' or add 'san' to the name and the title unnecessarily. Use '[Name]-kun' or 'Otouto-san', but usually not both in the same breath unless you are being extremely specific.

❌ 田中さんの弟のさん...
✅ 田中さんの弟さん...

A subtle mistake is using 'otouto-san' for an older brother. The terms for older siblings are completely different (お兄さん - oniisan). In Japan, the distinction between older and younger is vital. Calling an older brother 'otouto-san' is not just a vocabulary error; it's a disruption of the birth order hierarchy which is deeply respected in Japanese culture.

❌ (Talking to a friend about their big brother) 弟さんは元気ですか？
✅ お兄さんは元気ですか？

Kanji Confusion: Do not confuse 弟 (otouto) with 弟 (deshi - apprentice/disciple) which uses the same kanji but is part of the word 弟子 (deshi). While related (a disciple is like a 'younger brother' in a craft), 'otouto-san' specifically means a biological or legal younger brother.

Lastly, learners sometimes forget the 'san' when talking to someone they don't know well. While you might omit 'san' for your own brother, omitting it for someone else's brother makes you sound rude or overly familiar. When in doubt, always include the 'san'.

While 弟さん (otouto-san) is the most common term, Japanese has several other ways to refer to a younger brother depending on the level of formality and the relationship between the speakers.

弟 (Otouto): This is the humble/plain form. Use this for your own younger brother when talking to people outside your family. It is the base word without any honorifics.
弟様 (Otouto-sama): This is an extremely formal version. You might hear this in historical dramas, or if you are speaking to someone of very high social status (like royalty or a high-ranking CEO) about their family. It is rarely used in daily life.
ご弟君 (Gotei-kun): A formal, somewhat literary way to refer to someone else's younger brother. You might see this in formal letters or wedding invitations. The 'go' (ご) is a prefix for respect, and 'tei' is the On-yomi reading of 弟.

Comparison:
Casual: 弟 (otouto) - My brother
Polite: 弟さん (otouto-san) - Your brother
Very Formal: ご弟君 (gotei-kun) - Your honorable brother

In casual settings, if you are close friends with the person and their younger brother is much younger than you, you might use 弟君 (otouto-kun). This replaces the polite 'san' with 'kun', which is friendlier and often used for younger males.

義弟 (Gitei): This means 'younger brother-in-law'. While 'otouto-san' can also be used for a brother-in-law in conversation, 'gitei' is the specific technical term used in legal or formal contexts.

末の弟 (Sue no otouto) - My youngest brother.
If you are talking about someone else's youngest brother: 末の弟さん.

Understanding these alternatives helps you fine-tune your Japanese to the specific social situation. 'Otouto-san' remains your safest bet for 90% of conversations, but knowing 'otouto' for yourself and 'gotei' for formal writing will make your Japanese sound much more natural and sophisticated.

How Formal Is It?

Fun Fact

The kanji 弟 depicts a string wrapped around a pole, representing order or sequence. It's like a visual metaphor for the 'order' of birth in a family.

Pronunciation Guide

UK əʊ-təʊ-təʊ-sæn

US oʊ-toʊ-toʊ-sɑːn

In Japanese, pitch accent is used rather than stress. For 'otouto', the pitch is typically low on 'o' and high on 'tou-to'. The 'san' suffix is usually flat or follows the preceding pitch.

Rhymes With

Imouto-san Oniisan Oneesan Okousan Obousan Chousan Yousan Kousan

Common Errors

Pronouncing 'otouto' as 'ototo' (forgetting the long vowels).
Stress-accenting the 'san' too heavily.
Mixing up the 'o' and 'u' sounds in the middle.
Pronouncing it like 'otto' (husband).
Failing to elongate the 'o' sounds correctly.

Difficulty Rating

Reading 2/5

The kanji 弟 is basic but has a specific stroke order. Recognizable at A2 level.

Writing 3/5

Writing 弟 requires attention to the middle strokes to avoid looking like other kanji.

Speaking 1/5

Very easy to say. Just four syllables + san.

Listening 2/5

Easily distinguishable from 'oniisan' or 'imoutosan'.

What to Learn Next

Prerequisites

弟 (otouto) さん (san) 私 (watashi) あなた (anata) 家族 (kazoku)

Learn Next

お兄さん (oniisan) お姉さん (oneesan) 妹さん (imoutosan) ご両親 (goryoushin) 奥さん (okusan)

Advanced

義弟 (gitei) 舎弟 (shatei) 弟弟子 (otoutodeshi) ご弟君 (goteikun) 末弟 (mattei)

Grammar to Know

Honorific Suffixes (~san, ~kun, ~sama)

田中さん、健太くん、お客様

Uchi-Soto Kinship Terms

母 (haha) vs お母さん (okaasan)

Possessive Particle 'no'

私の弟 vs あなたの弟さん

Existence verbs 'imasu/arimasu'

弟さんがいます。

Giving and Receiving Verbs

弟さんにプレゼントをあげました。

Examples by Level

田中さんの弟さんは学生です。

Mr. Tanaka's younger brother is a student.

Uses the basic [Name] + no + [Family Member] + wa + [Noun] + desu pattern.

弟さんは何歳ですか？

How old is (your) younger brother?

The subject 'your' is implied by the context and the use of 'san'.

これは私の弟です。

This is my younger brother.

Note the absence of 'san' when referring to one's own brother.

弟さんはどこにいますか？

Where is (your) younger brother?

Uses the existence verb 'imasu' for people.

弟さんは背が高いですね。

(Your) younger brother is tall, isn't he?

Adds 'ne' at the end for agreement.

あそこに弟さんがいます。

(Your) younger brother is over there.

Uses 'asoko' (over there) and 'imasu'.

弟さんはテニスが好きです。

(Your) younger brother likes tennis.

Uses the 'ga suki desu' pattern for likes.

佐藤さんの弟さんは元気です。

Mr. Sato's younger brother is doing well.

Uses 'genki' as an adjective.

弟さんは、毎日何をしますか？

What does (your) younger brother do every day?

Uses 'nani o shimasu ka' for habits.

弟さんは日本料理が食べられますか？

Can (your) younger brother eat Japanese food?

Uses the potential form 'taberareru'.

弟さんに誕生日プレゼントをあげました。

I gave a birthday present to (your) younger brother.

Uses the particle 'ni' for the recipient.

弟さんはお兄さんに似ていますね。

(Your) younger brother looks like (your) older brother, doesn't he?

Uses 'nite imasu' for resemblance.

弟さんは車を運転することができますか？

Can (your) younger brother drive a car?

Uses 'koto ga dekimasu' for ability.

弟さんは英語を勉強しています。

(Your) younger brother is studying English.

Uses the continuous form 'te-imasu'.

弟さんはもう結婚していますか？

Is (your) younger brother married already?

Uses 'kekkon shite imasu' for state of being.

弟さんはどこで働いていますか？

Where does (your) younger brother work?

Uses 'doko de hataraite imasu ka'.

弟さんは、お父さんの仕事を手伝っているそうですね。

I heard that (your) younger brother is helping with (your) father's work.

Uses 'sou desu ne' for reported information.

弟さんは、来年大学を卒業する予定です。

(Your) younger brother is scheduled to graduate from university next year.

Uses 'yotei desu' for plans/schedules.

弟さんは、スポーツなら何でも得意だそうですね。

I heard (your) younger brother is good at any sport.

Uses 'nara' for 'if it's.../when it comes to...'.

弟さんに会うのは、今回が初めてです。

This is the first time I've met (your) younger brother.

Uses 'no wa ... hajimete desu' for first experiences.

弟さんは、お姉さんとは性格が全然違いますね。

(Your) younger brother's personality is completely different from (your) older sister's.

Uses 'to wa ... chigaimasu' for comparison.

弟さんは、将来海外で働きたいと言っていました。

(Your) younger brother was saying he wants to work abroad in the future.

Uses 'to itte imashita' for quoting past speech.

弟さんは、料理を作るのがとても上手だそうですよ。

I heard (your) younger brother is very good at cooking.

Uses 'no ga jouzu' for being good at an activity.

弟さんは、最近一人暮らしを始めたらしいです。

It seems (your) younger brother started living alone recently.

Uses 'rashii' for 'it seems/I heard'.

弟さんは、どんなに忙しくても毎日ジョギングを欠かさないそうです。

I heard that no matter how busy (your) younger brother is, he never misses his daily jog.

Uses 'donna ni ... temo' for 'no matter how'.

弟さんは、小さい頃からずっと医者になりたがっていたんですか？

Has (your) younger brother wanted to be a doctor since he was little?

Uses 'tagaru' to express a third person's desire.

弟さんは、お仕事でよく海外出張に行かれるそうですね。

I heard (your) younger brother often goes on overseas business trips for work.

Uses the honorific form 'ikareru'.

弟さんは、自分の意見をはっきり言うタイプの方ですね。

(Your) younger brother is the type of person who states his opinion clearly.

Uses 'kata' (polite for person) and 'taipu'.

弟さんは、お母様想いのとても優しい方だと伺っております。

I have heard that (your) younger brother is a very kind person who thinks of his mother.

Uses 'ukagatte orimasu' (humble for 'I have heard').

弟さんは、今回のプロジェクトで中心的な役割を果たしたそうですね。

I heard (your) younger brother played a central role in this project.

Uses 'yakuwari o hatasu' (to play a role).

弟さんは、ピアノのコンクールで優勝されたことがあるそうですよ。

I heard (your) younger brother has won a piano competition before.

Uses the honorific past form 'sareta'.

弟さんは、いつも冷静沈着で頼りがいがありますね。

(Your) younger brother is always calm and composed, and very reliable.

Uses the four-character compound 'reisei-chinchaku'.

弟さんは、学術界でも一目置かれる存在になっていらっしゃいますね。

Your younger brother has become a highly respected figure even in the academic world.

Uses the idiom 'ichimoku okareru' (to be highly regarded).

弟さんは、伝統文化の継承に並々ならぬ情熱を注いでいらっしゃるとか。

I hear your younger brother is pouring extraordinary passion into the succession of traditional culture.

Uses 'naminaminaranu' (extraordinary) and 'toka' (I heard).

弟さんは、若くして起業され、多方面でご活躍されているそうですね。

I heard your younger brother started his own business at a young age and is active in many fields.

Uses 'go-katsuyaku' (honorific for 'active/success').

弟さんは、その誠実な人柄ゆえに、多くの方から慕われていらっしゃいます。

Because of his sincere personality, your younger brother is adored by many people.

Uses 'yue ni' (because of) and 'shitawarete' (to be adored).

弟さんは、ご自身の信念を貫き通す強い意志をお持ちですね。

Your younger brother possesses a strong will to stick to his own beliefs.

Uses 'tsuranuki-toosu' (to carry through to the end).

弟さんは、語学が堪能で、数カ国語を自由自在に操られるそうですよ。

I heard your younger brother is proficient in languages and can handle several languages freely.

Uses 'tannou' (proficient) and 'jiyu-jizai' (freely).

弟さんは、芸術的な感性が豊かで、素晴らしい作品を数多く残されています。

Your younger brother has a rich artistic sensibility and has left behind many wonderful works.

Uses 'kansei ga yutaka' (rich sensibility).

弟さんは、周囲の期待に違わず、見事な成果を収められましたね。

As expected by those around him, your younger brother achieved brilliant results.

Uses 'kitai ni tagawazu' (meeting expectations).

弟さんは、社会の構造的な課題に対して、鋭い洞察力を持って提言されています。

Your younger brother is making proposals with sharp insight regarding structural issues in society.

Uses 'dou-satsu-ryoku' (insight) and 'teigen' (proposal).

弟さんは、かつての恩師の遺志を継ぎ、研究に心血を注いでいらっしゃいます。

Your younger brother is following the dying wishes of his former mentor and pouring his heart and soul into research.

Uses 'shinketsu o sosogu' (to pour heart and soul).

弟さんは、謙虚な姿勢を崩さず、常に自己研鑽に励んでいらっしゃいますね。

Your younger brother never loses his humble attitude and is always striving for self-improvement.

Uses 'jiko-kensan' (self-improvement/study).

弟さんは、多忙な日々を送りつつも、地域社会への貢献を忘れない方です。

While leading a busy life, your younger brother is someone who never forgets his contribution to the local community.

Uses 'tsutsu mo' (while/despite).

弟さんは、逆境に立たされても決して屈しない、不屈の精神をお持ちです。

Your younger brother possesses an indomitable spirit that never yields even when faced with adversity.

Uses 'fukutsu no seishin' (indomitable spirit).

弟さんは、その卓越した指導力で、組織を新たな高みへと導かれました。

With his outstanding leadership, your younger brother led the organization to new heights.

Uses 'takuetsu shita' (outstanding).

弟さんは、古今東西の歴史に精通し、博学多才な人物として知られています。

Your younger brother is well-versed in the history of all times and places and is known as a man of great erudition and talent.

Uses 'kokon-touzai' (all times and places) and 'hakugaku-tasai' (erudite).

弟さんは、物事の本質を見抜く眼力があり、その決断には一点の曇りもありません。

Your younger brother has the eye to see the essence of things, and there is not a single cloud of doubt in his decisions.

Uses 'ganriki' (insightful eye) and 'itten no kumori mo nai' (no cloud/flaw).

Common Collocations

弟さんがいる

弟さんに似ている

弟さんの名前

弟さんと遊ぶ

弟さんへのプレゼント

弟さんの学校

弟さんの結婚

弟さんを連れてくる

弟さんに会う

弟さん想い

Common Phrases

弟さんはお元気ですか？

— Is (your) younger brother doing well? A standard polite greeting.

久しぶり！弟さんはお元気ですか？

弟さんによろしく。

— Give my regards to (your) younger brother.

じゃあね。弟さんによろしくお伝えください。

弟さんがいらっしゃいますか？

— Do you have a younger brother? (Very polite)

佐藤様、弟さんがいらっしゃいますか？

弟さんとそっくりですね。

— You look just like (your) younger brother.

二人とも、弟さんとそっくりですね。

弟さんは何年生ですか？

— What grade is (your) younger brother in?

弟さんは今、何年生ですか？

弟さんはおいくつですか？

— How old is (your) younger brother? (Polite)

弟さんはおいくつになられましたか？

弟さんの分もどうぞ。

— Please take some for (your) younger brother too.

お菓子、弟さんの分もどうぞ。

弟さんがうらやましいです。

— I am jealous of (your) younger brother (having such a good sibling).

そんなに優しいお姉さんがいて、弟さんがうらやましいです。

弟さんと仲がいいですね。

— You get along well with (your) younger brother, don't you?

いつも一緒で、弟さんと仲がいいですね。

弟さんの影響で...

— Because of (your) younger brother's influence...

弟さんの影響で、サッカーを始めたんですか？

Often Confused With

弟さん vs お兄さん (oniisan)

Don't confuse younger (otouto) with older (ani).

弟さん vs 夫 (otto)

Sounds similar but means 'husband'.

弟さん vs 妹さん (imoutosan)

Don't confuse brother (otouto) with sister (imouto).

Idioms & Expressions

"弟分"

— A person treated like a younger brother, often in a mentorship or gang context.

彼は私の弟分のような存在です。

Informal

"兄弟は他人の始まり"

— Siblings are the beginning of strangers (meaning siblings often grow apart).

弟さんとも、大人になると「兄弟は他人の始まり」と言いますからね。

Proverb

"兄たり難く弟たり難し"

— Hard to tell who is the elder and who is the younger (meaning two people are equally excellent).

お二人とも優秀で、まさに「兄たり難く弟たり難し」ですね。

Literary

"弟を売る"

— To betray one's younger brother (rarely used literally, usually in stories).

彼は自分の利益のために弟を売った。

Dramatic

"末の弟"

— The baby of the family (male).

弟さんの中でも、末の弟さんは特に可愛いでしょう。

Neutral

"内弁慶の外地蔵"

— A lion at home, a mouse abroad (often said of younger brothers who are cheeky at home).

弟さんは、家では元気なのに外では静かなんですね。

Idiomatic

"手がかかる弟"

— A younger brother who requires a lot of care or causes trouble.

弟さんは手がかかるほど可愛いと言いますよ。

Common Expression

"弟の七光り"

— Basking in the reflected glory of a younger brother (variation of 'parent's glory').

有名な弟さんがいて、弟の七光りですね。

Sarcastic

"可愛い弟"

— A phrase used to describe a brother one is fond of.

弟さんは本当に可愛い弟さんですね。

Affectionate

"しっかり者の弟"

— A reliable younger brother (often contrasting with a less reliable older sibling).

弟さんはしっかり者で、お兄さんを助けていますね。

Complimentary

Easily Confused

弟さん vs 弟子 (deshi)

Uses the same first kanji 弟.

Deshi means apprentice or disciple, while Otouto is a sibling.

彼は私の弟子です。

弟さん vs 音 (oto)

The first part of 'otouto' sounds like 'oto'.

Oto means sound, not a person.

変な音がしました。

弟さん vs 乙 (otsu)

The kanji 乙 looks slightly like a simplified 弟.

Otsu is a ranking term (second/B) or slang for 'good job'.

お疲れ様（おつ）。

弟さん vs お父さん (otoosan)

Starts with 'oto' and ends with 'san'.

Otoosan is father; Otoutosan is younger brother. Listen for the 'u'.

お父さんは元気ですか？

弟さん vs 弟分 (otoutobun)

Contains the word 'otouto'.

Refers to a 'brother-like' figure, not a biological brother.

彼は私の弟分です。

Sentence Patterns

[Name]さんの弟さんです。

田中さんの弟さんです。

弟さんはいますか？

弟さんは[Noun]が好きです。

弟さんはサッカーが好きです。

弟さんに[Object]をあげます。

弟さんに本をあげます。

弟さんは[Verb-te]います。

弟さんは東京で働いています。

弟さんは[Verb]そうです。

弟さんは明日来るそうです。

弟さんは[Adjective]方です。

弟さんはとても親切な方です。

弟さんは[Verb-honorific]。

弟さんは海外に住んでいらっしゃいます。

Word Family

Nouns

弟 (otouto) - younger brother

兄弟 (kyoudai) - siblings/brothers

義弟 (gitei) - younger brother-in-law

舎弟 (shatei) - younger follower

弟分 (otoutobun) - person like a younger brother

兄 (ani) - older brother

お兄さん (oniisan) - someone else's older brother

妹 (imouto) - younger sister

お母さん (okaasan) - mother

お父さん (otoosan) - father

How to Use It

frequency

Extremely high in daily conversation.

Common Mistakes

Watashi no otouto-san wa gakusei desu. → Watashi no otouto wa gakusei desu.
You should not use honorifics (-san) for your own family when speaking to outsiders. It sounds like you're bragging or being weirdly formal.
Tanaka-san no ototo wa nan-sai desu ka? → Tanaka-san no otouto-san wa nan-sai desu ka?
Missing the long vowels (u) and the honorific (san) makes the sentence sound childish and slightly rude.
Confusing 弟 (otouto) with 妹 (imouto). → Using 弟 for boys and 妹 for girls.
Younger brother and younger sister are distinct words. Make sure you use the correct gender term.
Using 'Otouto-san' for an older brother. → Use 'Oniisan' for older brothers.
Birth order is extremely important. Calling an older brother 'otouto' is a factual error in Japanese social terms.
Saying 'Otouto-san-san'. → Just 'Otouto-san'.
Learners sometimes double up on honorifics by accident. The 'san' in 'otouto-san' is sufficient.

Tips

Uchi-Soto Rule

Always remember: Humble (Otouto) for your family, Polite (Otouto-san) for others. This is the golden rule of Japanese kinship terms.

Long Vowels

Ensure you pronounce both long 'o' sounds. 'O-to-to' sounds like 'fish' (toto) in baby talk. It must be 'O-too-too'.

Use the Name

If you know the brother's name, it's often more natural to say '[Name]-kun' or '[Name]-san' instead of just 'Otouto-san'.

Stroke Order

Pay attention to the stroke order of 弟. The vertical line goes through the middle at a specific point. Practice makes perfect!

Particle 'No'

Don't forget the 'no' when linking a name: 'Tanaka-san NO otouto-san'. It shows the relationship clearly.

Photos

When looking at a friend's childhood photo, 'Otouto-san, kawaii desu ne!' is a great compliment.

Match the Verb

If you use 'Otouto-san', make sure your verb ends in 'desu' or 'masu' to keep the politeness level consistent.

Opposites

Learn 'Otouto-san' and 'Oniisan' together. They are the two halves of the male sibling world.

Listen for 'San'

In a busy conversation, the 'san' is your best clue that the speaker is not talking about their own family.

Formal Letters

For formal greeting cards (like New Year's), 'Gokazoku no皆様' (everyone in your family) is often safer than listing siblings.

Memorize It

Mnemonic

Think of 'Otouto' as 'Oh, too toe' (he's small and follows your toes). Adding 'san' makes him the 'Honorable Toe-Follower'.

Visual Association

Imagine a small boy following a taller boy, holding a sign that says 'I'm second!' and wearing a hat with 'SAN' written on it.

Word Web

Family Younger Male Polite Respect Siblings Honorific Social distance

Challenge

Try to identify three famous characters in anime who are younger brothers and refer to them as '[Name]-san no otouto-san'.

Word Origin

The word 'otouto' comes from 'oto' (younger/later) and 'hito' (person). Historically, it referred to any younger sibling regardless of gender, but it became gender-specific over time.

Original meaning: Younger person / Later-born person.

Japonic (Japanese).

Cultural Context

Be careful not to use 'otouto-san' if you aren't sure the person is actually the younger brother. If they are the older brother, use 'oniisan'.

In English, we just say 'your brother'. We don't have a specific word for 'someone else's younger brother' that we use in every conversation. This is a major difference in how family is perceived.

Alphonse Elric (Fullmetal Alchemist) - often referred to as 'otouto' by Edward. Sasuke Uchiha (Naruto) - the tragic younger brother figure. Luigi (Mario Bros) - the quintessential younger brother.

Practice in Real Life

Real-World Contexts

Meeting a friend's family

弟さんは何歳ですか？
弟さんはお名前は何ですか？
弟さんはテニスが上手ですね。
弟さん、初めまして。

Office small talk

弟さんも同じ会社ですか？
弟さんはどこにお住まいですか？
弟さんのご結婚、おめでとうございます。
弟さんによろしくお伝えください。

Asking for someone at the door

弟さんはいらっしゃいますか？
弟さんはいつ戻りますか？
弟さんにこれを渡してください。
弟さんに用事があります。

Looking at photos

これが弟さんですか？
弟さんはお父さんに似ていますね。
弟さんは背が高いですね。
弟さんは何人いますか？

Talking about gifts

弟さんの分もお土産を買いました。
弟さんは何が好きですか？
これは弟さんへのプレゼントです。
弟さんに喜んでもらえるといいですね。

Conversation Starters

"弟さんは、今何を勉強しているんですか？"

"弟さんと一緒に旅行に行ったことはありますか？"

"弟さんは、あなたと性格が似ていますか？"

"弟さんは、どんなスポーツが好きなんですか？"

"弟さんは、もうお仕事を探しているんですか？"

Journal Prompts

友達の弟さんについて、知っていることを書いてみましょう。

もしあなたに弟さんがいたら、一緒に何をしたいですか？

田中さんの弟さんに会った時の会話を想像して書いてください。

「弟さん」と「弟」の使い分けについて、例文を作って説明してください。

あなたの国の「弟」に対する呼び方と、日本の「弟さん」の違いを書いてください。

Frequently Asked Questions

10 questions

Generally, no. You would call him by his name or just 'Otouto' when talking to others. Calling him 'Otouto-san' sounds like you are being overly formal or sarcastic to your own family.

Using 'Otouto-san' is the perfect polite way to refer to him if you don't know his name. For example: 'Otouto-san wa nan-sai desu ka?'

Yes, if you are close with the family and the brother is younger than you. It sounds friendlier and less formal than 'Otouto-san'.

You can say 'Sue no otouto-san' (末の弟さん).

Yes, in casual conversation, it is very common to use 'Otouto-san' for a younger brother-in-law. 'Gitei' is more for formal documents.

'Otouto' is for your own brother (humble). 'Otouto-san' is for someone else's brother (polite).

No, it elongates the 'o' sound. It's 'o-too-too', not 'o-to-to'.

Yes, as long as he is the younger brother *of your friend*. Politeness is relative to the sibling relationship, not just your own age.

It is written as おとうとさん.

Yes, the one born second is the 'otouto', even if it's just by a few minutes.