Translation guide
In Japanese, there is no single everyday word that directly translates to 'siblings'. Instead, you refer to brothers and sisters using specific terms that indicate relative age and sometimes gender. The most common way to talk about your own siblings is to use 兄弟 (kyoudai) for 'brothers' or 'siblings in general', and 姉妹 (shimai) for 'sisters'. When asking about or referring to someone else's siblings, you use honorific forms like ご兄弟 (go-kyoudai) or ご姉妹 (go-shimai).
You want to talk about your brothers and sisters without specifying gender or age.
Literally 'brothers', but commonly used as a generic term for 'siblings' when the gender mix is unknown or includes at least one brother. Can also refer to just brothers.
私は兄弟が三人います。
I have three siblings.
兄弟はいますか？
Do you have siblings?
Used when you know all siblings are female. Not used as a generic term for mixed-gender siblings.
You want to ask about or mention the siblings of someone you are not close to, or in a formal situation.
Polite form of 兄弟. Use when asking about someone else's siblings, regardless of gender mix.
ご兄弟は何人ですか？
How many siblings do you have?
You need to distinguish between older and younger brothers or sisters.
Older brother (your own). Use お兄さん (おにいさん) for someone else's older brother.
You want to say how many siblings you have, or ask about the number.
Standard pattern to say 'I have N siblings'. Replace [N] with the number. Use 兄弟 even if you have sisters, unless all are female.
兄弟が四人います。
I have four siblings.
Use only if all siblings are female.
You want to ask someone if they have siblings, or how many.
Casual/polite way to ask 'Do you have siblings?'. For more politeness, use ご兄弟はいますか？
兄弟はいますか？
Do you have siblings?
While 兄弟 can be used as a generic term for siblings, it is not appropriate when you know all siblings are female. In that case, use 姉妹 (しまい) or specify individually.
彼女には姉妹が二人います。
She has two sisters.
兄弟 (きょうだい) is the default word for 'siblings' and can include both brothers and sisters. 姉妹 (しまい) specifically means 'sisters' and is used only when all siblings are female. When in doubt, 兄弟 is safer.
In Japanese, you often refer to your own siblings by name or title (like お兄ちゃん) when speaking within the family. When talking to outsiders, use the humble forms (兄, 姉, 弟, 妹) to refer to your own siblings, and honorific forms (お兄さん, お姉さん, 弟さん, 妹さん) for others' siblings.
I have two sisters.
Polite form of 姉妹. Use when you know the siblings are all female.
ご姉妹はお元気ですか？
How are your sisters?
兄は東京に住んでいます。
My older brother lives in Tokyo.
Younger brother (your own). Use 弟さん (おとうとさん) for someone else's younger brother.
弟は学生です。
My younger brother is a student.
Older sister (your own). Use お姉さん (おねえさん) for someone else's older sister.
姉は看護師です。
My older sister is a nurse.
Younger sister (your own). Use 妹さん (いもうとさん) for someone else's younger sister.
妹は高校生です。
My younger sister is a high school student.
姉妹が三人います。
I have three sisters.
Polite way to ask 'How many siblings do you have?'
ご兄弟は何人ですか？
How many siblings do you have?