What do you do when old friends always ask you about your ex?

For a long time in college I was with a guy who was like the character of "Fun Bobby" on "Friends": he was the life of every party, and everyone adored him, and they didn't know (and I didn't know at first) that he was really troubled and could not form lasting attachments very easily. We had a huge breakup when I found he was constantly cheating on me, and when he moved out of NYC (I did eventually too), he cut out almost all his friends from that time too.

I hear about him every so often when other people bring him up (his life is still a mess, but he lives in LA now), but he's a painful reminder of that broken tie in my life for the most part. But when friends from the period of my life in NYC contact me they always ask about him, and even when i say, "He's in LA and I barely keep in touch with him," they still want to ask me questions about him and why he's no longer friends with them. I feel like they only are still interested in me as a conduit to talk about him. I've even reminded some of them how badly he hurt me and how I don't like talking about him, and they STILL ask me about him.