My sons' biological father is against my fiance

My son just turned 4 and i have been with my fiance since my son was 13 months old. My son calls my fiance daddy. His biological father has visitation with my son and my son does call him dad as well. My problem is his biological father tells are son that my fiance is not his father and he is not allowed to call him dad. He also tells my son that my fiance is stupid and to not play with him. His biological father also tells my son he is not allowed to call my fiances' parents and grandparents grandma or grandpa. Im not sure how to handle this situation with my son or his biological father. How do i talk to both of them about it?

[Kevin Kennedy, Ph.D.]

Unfortunately, you are likely not to make much progress on this issue. If your son's father shows such insecurity and poor judgment that he would even say such things, he's likely not to change. All you can do is nicely speak with him about his remarks and how this puts his son in a very difficult position. With your son, who is too young to understand these things, it does make sense to say that sometimes, when parents are no longer together, one parent might have a hard time seeing another person in the household. Basically, if your son brings this matter up, focus more on drawing him out rather than on anything you might say in response. Be sure not to criticize his father - that would be wrong. Just focus on asking your son what he thinks about the situation. Ultimately, even though it will take time, he will make up his own mind about his relationships, regardless of what someone else has to say.