Yeah, you're right. It doesn't sound like much it sounds like too much actually. For a boy of 14 it is too early for heavy drinking and three years after he has to have some problems. You should help him in some indirect way I believe because he might have some reaction on you approaching directly. That is just my opinion. If you have time and you want to help and you are his best friend you should encourage some activities instead of going out. Be persistent in your wishes to try something else. Say you need some time off the city limits. Go hiking. Do things he used to love. Remind him that life is more than booze.