I always refer to the backstabbing,[when they are not present] friendly to your face [when talking about someone else] as musical chairs. I saw alot of this with DH and his ex and daughters.

My only advice is totally stay out of it. FACEBOOK seems to reconnect and maintain many relationships that would otherwise have fizzled out long ago. I limit mine to only my sister and my daughters.

DH divorced his wife almost 35 years ago. For some reason she is on every past and present relatives friend list. Family members that never met her have her on their friend list. All the more reason for me not to accept the many friend requests from DH's family members.

I just stay out of it all. As far as I am concerned---What happens in my life or my own family'y lives stays private. I share very little negative things with DH to repeat.

If it's the ex wife that has custody of the kids you might find its simply to keep her sweet. They might feel that if they don't get in with her then they won't see the kids as much, especially if you don't have the kids as much as BM does. Unfortunately it seems that a child belongs more to the mother than the father, it always has done. For instance my partner's family aren't exactly the best of friends with BM but they make an effort with her as she's the one looking after her kids and also the times they want to see them is when they're under her care as they work all weekend when partner has them. Whereas BM's parents never speak to partner now even though they knew him for nearly 15 years. But why would they, it's their daughter that has the children they can see their grandchildren whenever they want.