Are my friends just using me for my brother?

Okay I'm asking this on behalf of my friend -

Im 12, I like to read a lot, and I'm not your typical girl. I'm not all obsessed with boys make-up clothes etc. I get sort of annoyed being around those who are, which consists of pretty much every girl in my school. So, I prefer to be alone sometimes. I have a 16 year old brother. So other girls, he's hot and whatnot. To me he's just annoying and a pest. So my friends ask me if they can come over to hang out with me, then when they get here and he sees them he'll ask em to go watch a movie with him or whatever, and they just leave. Are they using me to get to him? Is that the only reason why theyre my friend, the only reason why they come over? And if so what do I do about it? Should I talk to them about it? if so what do I say? I'm just confused right now and dont know if theyre truly my friends or not

 
It's possible that that is the reason many of them first attempt to associate with them. Don't worry about it though. It has the benefit of allowing you to be exposed to many different 'friends' whom you wouldn't otherwise be exposed to and some of them may turn out to become real friends.

I think your putting the blame on the wrong persons. Your brother is the one whos taking them away from you. I have an older brother, and there is NO way he would have even talked to my 12 yr old girlfriends when he was 16, let alone ask them to watch a movie with him. So you should be talking to him, and telling him how you feel, not your friends!