You all should know that the situation with the Ex and his girlfriend isn't as totally bizarro as that last post makes it seem. We don't generally hang out together or anything, and I make a real effort to set boundaries for myself. We're all friendly, and my feelings for the Ex really do border on fraternal (what's the sisterly version of that? sororitorial?), so we will get together for holidays or kid-centric activities, and we'll help each other out if a schedule juggle is called for, but I do my best to stay out of their whole, y'know, thing.
It's a little complicated because of extenuating circumstances that I don't really want to go into in a public forum, but there has been, over the past few months, a little more of a familial "support" role on my part. Still, I'm being very careful about my boundaries and in general, I say the same things over and over: It'll be okay, you need to talk to each other, not to me.
So I'm not totally nuts. Just FYI.