1.
siblings; brothers and sisters
A gender-inclusive term for all siblings. Used in formal and official contexts to explicitly include both male and female siblings, unlike the more common 兄弟 which can be ambiguous.
Usage: 兄弟姉妹 is the explicitly gender-inclusive term for siblings, combining 兄弟 (brothers) and 姉妹 (sisters). It is commonly used on official forms and in formal writing.
In everyday speech, 兄弟 alone is often used as a gender-neutral term for siblings regardless of sex, but 兄弟姉妹 is preferred in official and precise contexts.