Best friends older brother

Ok for context I’m 21F my best friend is 23F and he’s 28 or 29M
I have known they’re family for over a decade, so basically her brother seen me grow up and our families were kind of intertwined (used to be neighbors)
I always had the biggest crush on him growing up then of course it faded.
I have been seeing him so often since hanging out with my friend a lot more and oh my fuckk I cannot stop thinking about him and just like what we can do. I always find so much attraction to things I shouldn’t do or have. I literally can’t stop lmfao I want to do something so bad but I feel it’s forbidden in a way.
Sometimes I feel like he feels the same way but I could be just so delusional. There has been times where I feel like he does things to have a convo or something with me since it’s not normal for us rlly cause we never had that close connection. Idk but I really want to do something just to try it but scared he’s gonna see me as a little sister or ugh idk. Needed to just get this off my chest