a male offspring having both parents in common with another offspring; a male sibling.

Also called half brother. a male offspring having only one parent in common with another offspring.

a stepbrother.

a male numbered among the same kinship group, nationality, race, profession, etc., as another; an associate; a fellow member, fellow countryman, fellow man, etc.

a fraternity brother.

Ecclesiastical .

( often initial capital letter ) a male numbered among the lay members of a religious organization that has a priesthood.

a man who devotes himself to the duties of a religious order without taking holy orders, or while preparing for holy orders.

brothers, all members of a particular race, or of the human race in general

All men are brothers.

Slang . fellow; buddy

Brother, can you spare a dime?

Informal . a black man; soul brother.

Slang . (used to express disappointment, disgust, or surprise).

noun

sister

noun

blood brother , kin , kinsperson , relation , relative , twin , amigo , chum , confidant , confidante , familiar , intimate , mate , pal , alliance , billy , blood , bro , brotherhood , bub , buddy , cadet , companionship , comrade , confraternity , confrerie , fellow , fellowship , fra , fraternity , friar , monk , peer , sibling , sodality