Should I Ask Him If He Likes Me?

I think you should talk to your friend first to find out what she thinks about your feelings, and you two can decide how this should be approached, if she likes the thought. Hope this helps, good luck.

If you can tell he likes you and your completely sure of this I mean 100% sure than ask him. Although, i will warn you if he doesn't feel this way about you then this could damage your friendship, it could become awkard and might upset your friendship with his sister. It will take a lot of debating. My advice to you would be to spend a little bit more time than usual with him and see what his his his actions are toward you, and when your sure pop the question, However I wouldn't out of nowhere go "do you like me more than a friend?" Casually get on to the subect of relationships and than ask. I hope this helped.  

I think you should. Since it is your best friends brother then you should ask her if it is okay. You in your heart know how you feel about him so I say go for it, if your friend tells you "yes" that is.

:) DO NOT GO RIGHT TO THE POINT!  Just take a few days to get to know him.... Then if you do like him and SURE ask him....!!
EVEN BETTER: MAYBE HE'LL SAY IT TO U!