It sounds like to me you’ve really hit it off with this guy.. I don’t see what the problem is. Unless of course you are a minor! As long as that’s not the case I would continue to take it slow and see where it goes. Your older brother is friends with him so if he was a sleeze I doubt your big bro would be cool with him crushing on his little sis. As far as the age difference is concerned, I’ve always believed (and I think there’s a lot of people who can back me up on this one) that men mature much slower than women do. For a lot of women dating men 8 to 10 years older is very necessary in order to really connect on an intellectual level. It’s just one of the many differences between men and women. So like I said tread slowly and have fun while your at it.. he seems like a great guy.
Best of luck!