When you get involved with a guy who has an ex-wife and kid(s), it's a package deal. The ex is going to be part of your life ( I know because I AM an ex-wife and my fiance has an ex-wife). The best thing you can do for your relationship is to try to understand her and even befriend her. Chances are you have a lot more in common than you think you do, otherwise he wouldn't have been attracted to both of you in the first place. Her "crazyness" is probably just really fear. Depending on how long they have been legally divorced, she may not be emotionally divorced from him yet. She's going through the "I don't want you, but you can't have a life without me either" stage. Even if she's the one who left, it's really hard to see your ex moving on and being happy without you. The bottom line is that if you truly trust in your relationship with your fiance, then YOU have to be the mature one ( remember you agreed to take on a package deal, right?) Let the ex-wife grieve for the end of this relationship. Let her be "crazy" for a while. Show your grace, maturity and flexibility. Know your boundries when it comes to the child. Don't step on her maternal toes. Most of all, don't flaunt your relationship in her face. Stay in the background for a while. Let him have time alone with his child without you there. Don't go with him to pick up the child for visitation. Eventually she will come around once she doesn't see you as a threat to the well-being of her child. As long as there is a child involved, they will be co-parents. The child needs both parents to be friendly or at least civil to each other. As far as family goes, you can't ask them to stop talking to her. He's the mother of their grandchild. Even if they truly don't like her, if they alienate her, they may lose contact with the child. If you are truly secure with this man then it shouldn't be a problem. If you can't do this, then you should get out of this relationship and find a man with no kids. Stepfamily siturations are VERY complex and VERY difficult. They aren't for the faint of heart. Over 60% of second marriages end in divorce within the first 3 years and the primary issue is the children and the ex. Get yourself some good books on stepfamily relationships and divorce and start reading. Or better yet, go to family counseling BEFORE you get married. Good luck