your post is really really graphic but
1. "First, I was wondering, with the shaving and the thrusting and the grabbing and the showing, do you think Brent is gay"
the thrusting, grabbing and showing might be because hes curious but he might be gay or bi. and shaving has nothing to do with your sexuality
2. "second, id it odd that my penis doubles theirs? Will it keep growing, seeing that I'm actually not very far through puberty compared to Brett? Will it be too big?"
it might keep growing but i dunno for sure and i dont know if itll be "too big" because everyone has their own idea of big and people also have their own preferences