Hi A., First of all welcome to Oklahoma. How old is your oldest child, and was it his/her choice to live with dad? Its sad to know that your children are separted like that. Well, from past experience, I think when the children turn 12 or 13, they can refuse to see him.There is a 800 number you can call if he is $5000.00 behind in back child support. I think its 1-800-kids. His rights can be terminated "if" he has no contact or no support for one year. This was told to my daughter by a lawyer. If you feel your children are in danger when your x has them, you could possibly contact child welfare, but don't count on any action. I have dealt with that situation many times. I was told a long time ago by a court offical that even though my x did not pay child support he was still allow to see kids. I told them not a chance, of course I would be in contempt of court, but I didn't care. I know its hard for you and kids, but the law is funny, unless you have money,its ok for the dad to skip out on his responsibilities, but you have to hold up to yours. Please let me know how its going, it really bothers me how parents manage to deny their children. Your children knows who loves them,the kids see more than anyone can imagine. Your x will be the one to suffer in the end. Keep your head up, just love your kids and be proud of them. I would love to keep in contact with you, its always nice to have some support.