I have had similar problems in the past with friends and family, unfortunatly I just ended up losing my temper and just physicaly fighting with them.
Bad Bad mistake. Anyway, the best thing I can sujest is talking to him, about it, or tell somebody to make him back off.
I have difficulty dealing with these types of situations so I aint the best to be giving advise. Just try not to react to any comments etc when he is around.
Maybe he will get bored and lay off. Try not to do what I do and start fighting with people 9 out of ten it goes horribly wrong. I have 2 cousins who wont talk to me because of this.
So I guess I have told you what you SHOULDN'T do i guess.