A term used to describe a good friend that you have known almost your whole life. The word "brother" is used because the friend is extremely close to you to the point that he is almost like your brother--but from a different mother. And that rhymes. And you know that rhymes. Admit it!
"What's happenin' my brother from another mother?"
A theory which states that a man must keep his personal life (i.e. friends) separate from his relationship side (i.e. girlfriend). Should the two worlds come into contact with each other (by means of his girlfriend becoming friends with his friends), both worlds blow up.
"If Relationship George walks through that door, he will kill Independent George! A George divided against itself, cannot stand!" - George Costanza