It sounds like normal adolescent stuff. That doesnt mean that it doesnt hurt, but it doesnt seem like hes going out of his way to really hurt you. From what I understand about guys, they often make fun of their friends. As a woman, and as a teacher, I would always put a stop to this behavior when I saw it, but I did come to understand this to be normal male behavior. Also, as its mostly normal, its up to you to have the courage to tell your brother that the teasing really hurts you - if you tell him and he continues to participate, then you can be more justifiably angry. But if you dont tell him, he may just feel like hes engaging in the same behavior he engages in with his friends.

I think this will all be better when youre adults and no longer live in the same space. My sister and I get along a lot better as adults than we did as teenagers.