brother

a male with the same parents as someone else; "my brother still lives with our parents"

a male person who is a fellow member (of a fraternity or religion or other group); "none of his brothers would betray him"

a close friend who accompanies his buddies in their activities

used as a term of address for those male persons engaged in the same movement; "Greetings, comrade!"

(Roman Catholic Church) a title given to a monk and used as form of address; "a Benedictine Brother"