名词亲兄弟，结拜兄弟

1. 结拜兄弟；歃血为盟的兄弟
A man's blood brother is a man he has sworn to treat as a brother, often in a ceremony which involves mixing a small amount of their blood.

noun

1. a male sworn (usually by a ceremony involving the mingling of blood) to treat another as his brother

2. a male with the same parents as someone else

e.g. my brother still lives with our parents

Synonym: brother