My little brother tries to fit in with what he believes is the popular kids. Most people realize that these are just scum with overinflated egos, but not my brother. I'd tell him to ignore those morons and stick with his real friends but he treats any advice from me with contempt. Now, these are the type of people to gay-bash, so I suspect that if I come out the teasing I suspect he already receives (not that he would ever tell me, but I'm not stupid. It's pretty easy to figure out) would increase tenfold.
You can lead a horse to water, but you can't make him think. Come out when you are ready and ignore the morons and what they might be teasing your brother about. If/when he sees them teasing him about you, he may finally realize that they aren't as cool as he thought they were and return to his real friends and stick up for his family (you). Then he will be the cool kid, whether he is popular or not.
