I think it is important to remember that people shoudn't be taking sides. They will have developed their own relationships with his family. Just because the couple parted ways should not force the cease of all communication between the extended family members.

Yes, it is hard. I have my own grief at the fact that my friends, family are still friends with my ex. Even my children have stayed friends with him, their step-father. It pains me to know all these people maintain contact with him. But the relationship I had with him is not the same as the relationship they had with them. The way I see it is that they will eventually come to realize what a jerk and idiot he is on their own and it is not for me to influence that.

Instead, concentrate on the building and forging of new realtionships and traditons.