Actually 2 computers on the same network usually have the same IP.
The "little brother" excuse just got old, if we believed everyone who said it no one would ever get banned for botting/macroing. We can't go to your house to verify, and even if we did verify that you really have a brother (which we wont), we wouldn't know really which one of you really did it. It's simpler that way, so if you have siblings playing make sure they understand the rules because those offense are punished by a ban on all related accounts. Same goes for lending items, if you lend something to someone and their accounts get banned your item is gone, so be careful whom you trust.