"...If the homies can't have none..."
So picture a guy in a situation with a girl where they are basically just messing around, not really anything serious. After a period of time, knowing that the girl is really feeling him, the guy is able to convince the girl into sleeping with his cousin AND one of his boys. Not at the same time (like a train), but on different occasions she sleeps with both of them.
Ok, at this point you may just be thinking wow, that's some #hoshit (or maybe those are just my thoughts).