My brother is really annoying and people complain about him to me, what should I do?

There's one thing you just can't change, and that's who your family is. You don't have to like him, but you should love him, despite his short comings. Or, you can disown him. You sound pissed that he keeps taking girls you like; maybe you should try to keep girls away from him, knowing that he gets a rise out of taking them from you. You don't have to carve out your lives together, or anything, just stay away from him.