Q. "My son's father left us five years ago. Since then, I have remarried to a lovely man. David, my husband, has tried hard to make friends with Nathan, and left all the disciplining to me. Yet, though we have been married three years, my son still refuses to do anything that my husband asks. How do I get him to listen to his step father?"

A. Children often feel at fault when their parents divorce, even though the problems are with the adults. Nathan most likely sees the situation as his dad leaving him, rather than you. If his dad doesn't visit, or is sporadic about it, this will only reinforce Nathan's belief. He feels abandoned, guilty and also angry. His biggest fear is probably that you will leave him too.

Having another man in the house only intensifies the problems. Nathan now knows that his parents won't be getting back together. It also means that David is getting attention from you as well. When you were single, he had you all to himself. No wonder he feels terrible.

Perhaps Nathan got on really well with David before you married. At that stage, he was just Mum's boyfriend. Then, he was fun to have around, and never tried to act bossy. Now he is living in the house like he owns it.

Making the transition from visitor to parent is often very tricky. The key to it is to be open and honest about it all. Communication is the key. Make time to talk together, regularly, in various combinations: you and Nathan, Nathan and David, and all three of you. Include your other children if you have any.

Let Nathan know that you are aware of his resentments, and confusion, and anger. Reassure him that David will never take his dad's place. It's perfectly normal for Nathan to love and miss his dad, even though you don't. Just be matter-of-fact about why you divorced and don't drag the kids into any parental battles.

At the same time, be clear about the fact that David is here because you love him and asked him to join your family. Tell Nathan that you don't love him any less and that he can like David without betraying his own dad.

You have to tell Nathan that David does have parental authority over him now. Whatever he asks him to do, he must do it. Don't let Nathan come to you and try to discount anything David requires from him. If you don't like something David is doing, take it up with him privately. In public you have to back him up. Nathan has to be aware that you and David are a couple now and stand together in family decisions.