Go easy on your brother. Maybe he's just jealous. Life is too short to be bickering all the time. My brother used to tease me and now I see my little guy (5½) teasing his little sister (2¼). I'm trying to put a stop to it.
Its great that you are passionate about bikes, but don't let it get in the way of family.
Your best bet is to
1. keep your mouth shut
2. get your license
3. buy your bike
4. don't brag about it and don't pay any attention to criticism
5. most importantly, HAVE FUN!!