Japanese Family Relationship Names Explained (English to Japanese Guide)

If you've ever tried to translate a family tree into Japanese, you've probably noticed something odd: there's no single word for "brother" or "grandmother." Japanese kinship terms are built around two things English speakers aren't used to thinking about - relative age and whose family you're talking about. Once you understand those two rules, the whole system clicks into place.

This guide walks through the core Japanese family relationship names, why there are often two versions of the same word, and how to use them correctly when you're labeling a family tree or just trying to talk about your relatives.

The Big Rule: Your Family vs. Someone Else's Family

Japanese has a built-in politeness system, and it applies directly to family words. You use one set of terms when talking about your own family (humble, plain form) and a different, more respectful set when talking about someone else's family - or when addressing your own relatives directly.

For example, you'd never call your own mother "okaasan" when describing her to a stranger in the humble register - you'd say "haha." But you'd call her "okaasan" to her face, and you'd always use "okaasan" for someone else's mother.

Relationship	Your family (plain)	Addressing them / someone else's family
Father	chichi	otousan
Mother	haha	okaasan
Grandfather	sofu	ojiisan
Grandmother	sobo	obaasan
Husband	otto / shujin	goshujin
Wife	tsuma / kanai	okusan
Son	musuko	musukosan
Daughter	musume	musumesan

This distinction matters most in formal or written contexts - in casual daily conversation, most families simply use "otousan" and "okaasan" for their own parents too.

Siblings: Age Comes First

Unlike English, Japanese has no neutral word for "brother" or "sister." You always specify whether the sibling is older or younger than you:

• Ani - older brother (own family) / oniisan - older brother, respectful
• Otouto - younger brother
• Ane - older sister (own family) / oneesan - older sister, respectful
• Imouto - younger sister

There's no separate respectful form for a younger sibling - "otouto" and "imouto" work in both contexts, since younger siblings aren't addressed with the same honorific weight as older ones. This age-first structure is a legacy of a family system that historically treated birth order as socially significant, and it still shapes how Japanese families talk about each other today.

Grandparents, Aunts, Uncles and Cousins

• Grandfather: sofu (own) / ojiisan (respectful)
• Grandmother: sobo (own) / obaasan (respectful)
• Uncle: oji (covers both father's and mother's brothers, and aunts' husbands)
• Aunt: oba (covers both father's and mother's sisters, and uncles' wives)
• Cousin: itoko - one word regardless of age or side of the family
• Nephew: oi
• Niece: mei

Notice that Japanese doesn't distinguish paternal from maternal uncles and aunts the way some languages do - "oji" and "oba" cover the whole extended family on both sides.

In-Laws

In-law terms are built by adding context rather than inventing new words in most cases:

• Mother-in-law / Father-in-law: giri no okaasan / giri no otousan ("giri no" means "by law" or "in-law"), though many families simply use okaasan/otousan directly once they're close
• Brother-in-law: giri no ani/otouto, depending on age relative to the speaker
• Sister-in-law: giri no ane/imouto

Building a Japanese Branch of Your Family Tree

If you're documenting a Japanese side of your family history, a few practical tips:

1. Record both the plain and respectful forms if you're labeling the tree for a Japanese-speaking relative - it shows care and avoids sounding overly formal or overly casual in the wrong context.
2. Note birth order explicitly for siblings, since the Japanese terms themselves already encode it - your tree will be more accurate if you capture who was older.
3. Keep uncle/aunt relationships tied to which parent's side they're on in your notes, even though Japanese doesn't require it - future generations researching the tree in English will want that clarity.

A tool like My rOoOts lets you attach these relationship labels directly to each person in your tree, so you're not relying on memory to keep the Japanese and English terms straight as the tree grows.

Frequently Asked Questions

Why does Japanese have separate words for older and younger siblings?

Japanese family structure has historically placed weight on birth order, particularly for inheritance and social roles within the household. That emphasis is baked directly into the vocabulary - there's simply no age-neutral word for "brother" or "sister" the way English has one.

What's the difference between chichi and otousan?

Both mean "father," but chichi is the humble form used when talking about your own father to someone outside the family, while otousan is the respectful form used to address your father directly or to refer to someone else's father.

Do Japanese people actually use two different words for their own parents in daily life?

In casual, everyday speech, most people call their own parents otousan and okaasan even at home. The plain forms (chichi, haha) mostly appear in more formal writing, business contexts, or when specifically distinguishing your family from someone else's.

Is there a single Japanese word for "cousin"?

Yes - itoko covers all cousins regardless of age, gender, or which side of the family they're on, which is simpler than the sibling and aunt/uncle system.

How do I say "in-laws" in Japanese?

Add "giri no" (meaning "by law") before the relevant family term, such as giri no okaasan for mother-in-law. In everyday speech, many families drop "giri no" once the relationship feels established and just use the direct family term.