In some relationships, there are fathers who struggle with Borderline Personality Disorder (BPD). While the disorder itself doesn't imply that a father is good or bad, it can mean that he faces some additional struggles. It's normal for someone with BPDs to have a primary attachment to his spouse and then to the child, instead of to the child and then the spouse.
That can create a problem in some cases. For instance, in a divorce, it's normal for a father with BPDs (fBPDs) to have a strong attachment to his spouse. When that spouse is no longer in the picture, the father may suddenly turn to the child and try to form an attachment that was previously not as strong.
This usually happens suddenly, which can mean that it comes across as controlling or abusive. The father may become competitive with the mother, use the child against his or her mother and work to intensify his bond with his child. The end result, and sometimes the goal, of this is to weaken the bond between the child and mother. Sometimes, the father actually attempts to alienate the child from the mother.
In certain cases, struggles with deciding how to raise your child could be due to fBPDs. For instance, if your ex-husband undermines your rules and allows your child to do things you won't allow, he could be making you out to be unreasonable in the eyes of your child.
Dealing with BPD is hard no matter who suffers from the condition in the family. It results in emotional abuse in many cases, and it's something you should be concerned about if you notice changes in your child's relationship with his or her father. Our site has more information on domestic abuse and other concerns you may have.