One of the worst types of divorce are the ones in which parental alienation occurs. The courts have held that a parent who alienates a child from the other parent or deliberately interferes with the relationship may be presumed to be an unfit custodial parent.
The problem in the courtroom is that it can take the wheels of justice a long time to grind to that result. In almost all such cases an attorney for the child is appointed, therapeutic visitation may be ordered, psychological testing and evaluation (forensics) may be required, but while all of that is going on, the innocent parent is still denied meaningful contact with the child. The child has been brainwashed to think that it is unsafe to be with the other parent, that the other parent has bad intentions and that the favored parent will be upset if the child has fun with the other parent.
Right now I am in the middle of representing a parent where the child calls the father by his first name, says that "Dad" is a name that has to be earned, claims that the father "hurt" me and while all this is going on, the therapists who recognize that the Mother is poisoning the children not only by her words but by her conduct, ie. what she says and what she doesn't say, her facial expressions and her total lack of interest in the other parent.
A father who was not seeking custody originally, now must seek custody to preserve his relationship and to protect the child from the harm of parental alienation. In addition, the cost of such a complicated case becomes huge and unless the parents have the financial resources, often the alienated parent gives up because of the cost.
My only advice is that the result will change as long as you don't give up. The court will overtime begin to restrict the favored parent, require more time with the alienated parent, and reduce the financial award to the interfering parent. If you are in such a fight it will require much stamina and confidence in your attorney to see you through to the end.