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.
A son of one's sibling, brother-in-law, or sister-in-law; either a son of one's brother (fraternal nephew) or a son of one's sister (sororal nephew).
A son of one's cousin or cousin-in-law