how can you tell?

Well, maybe you should just come out straight and ask him. I know that would probably be very hard for you to do because you've known him for so long, but that might be the best way to do it. Of course, he might not be completely honest if you do just ask him. To be honest, I think you should just let things unfold. Hey, if you have feelings for him too, maybe something could happen one day, only time will tell.

I'd want to think that he's interested in you because he's asking you about your boyfriend and friends, but I'd wonder why he hasn't made a move on you over the past 7-8 years. Was he in a relationship previously that he's just now overcoming and ready to move on? Do you have a deep connection...does he sit and talk to you looking in your eyes? I would look for some sort of body language that might help you see if he's in to you or just passing the time of day. Maybe it's that he's not confident and is worried about rejection that he hasn't made a move. If you feel comfortable, next time he brings up about boyfriends, I'd just come out and ask why he cares and if he's interesteed-maybe in even a joking matter just to feel him out. You don't want to lose your friendship with him, but at the same point, if you both care about each other and want to take it to the next level, you should say something rather than waiting another 7-8 years to ask.

I think he is in love with you but because you have a boyfriend already he is hesitant. Just be friends with him and observe his actions.

I think you should ask yourself if, in case he likes you, are you willing to accept this slow showing of feelings. And you also have to ask yourself if you care for him that way because if you don´t, there´s nothing to do.
It all depends on age. If you are both in your early teens, maybe it´s wonderful.
Take care