This dude is just not getting it...

So last night I was just minding my own business catching up on the 120ish blogs I follow when all of a sudden Facebook beeps at me and the tab flashes "J messaged you!" *audible groan* Evidently his now-live-in girlfriend discovered some old letter I'd wrote him before we were even dating that he kept all this time (damn near four years), and it got him thinking about me. And as ALWAYS, he wants to know when I'll be home next "so we can chill". Now chilling evidently means teaming up with the girl to play pool against him. I tried to seem marginally non-committal without being rude, but I just don't understand why this boy man boy thinks that we have a meeting up three years after we broke up to play pool with his new booskie kind of relationship. WE ARE NOT FRIENDS. We may have been friends before we dated, but I was a different person then. As the closest thing I've ever had to a regretted relationship with another person, there is no longer even the slightest bit of room for him in my life in any capacity...he just doesn't seem to be able to grasp that. I've only seen him twice since we broke up, the first time being my first break home, when I almost hooked up with him again, and then again the next summer, when I ran into him at the mall and he gave me a ride home, but nothing happened because he was already with his current girlfriend. He has asked me to hang out multiple other times, but I always find some way of blowing it off. It's not even a time heals all wounds scenario; nothing about him or potentially seeing him hurts at all--it's more like remembering him and us makes me feel awkward. I judge myself for having been with him [though my body doesn't, haha]. And I don't remember how I ever really related to him, and I'm not sure I want to. And maybe, just maybe, I don't know how to be friends with someone who knows what I taste like, even if I never want them down there again...

So how do I make it clear that I don't want to hang out when I come home this time, next time, or for the rest of ever? Or should I just bite the bullet and hang out with the two of them to show that I am a flexible person who can be friends with lots of different types of people, and so that I have experience having an amicable relationship with an ex? 
(...I suppose I should take it as a compliment that none of my three exes seem comfortable with the idea of not being able to have me marginally in their lives in some way, from C who came crawling and begging back [Negro please], this situation with J, and the things KO has said which may or may not come to fruition.)