I like a guy but I’m afraid of losing our friendship, what do I do?

I have known a guy all of my life and we have been best friends, but over the past few months I feel as though I have grown feelings for him. We don’t see each other often because I had to move away with family. This guy and all his family know our family very well, he’s like family friends I suppose. When we were in year 6 and 7 we used to make jokes that one day we would marry each other and stuff (Ik, really cringe). About a year after I found out he has had so many girlfriends and stuff and he had never told me even though we were best friends. I really want to confess but I’m scared what he’ll say. If he says no I will still have to see him as like I said before we are also family friends and I also don’t want to lose my best friend. What do I do??