Synonyms for brother

noun

1. A male sibling

   sibling, male sibling, stepbrother, half brother, foster brother, kinsman, blood relative, sib, big brother, kid brother*, bro*; see also relative.

2. A fellow member of a group

   associate, colleague, confrere, compatriot, fellow member, fellow human being, fellow creature, fellow man, soul brother, blood brother, buddy*; see also associate, friar.