A brother by blood: a brother-german or half-brother, as distinguished from step-brothers.
An unrelated male considered to share such a strong relationship generally.
An unrelated male considered to share a brother-like relationship established by a ceremonial sharing of blood in some cultures.
The stepson of one's parent who is not one's half-brother.
The son of one's stepparent who is not the son of either of one's biological parents.