What can a father do if mothers has moved kids out of state without permission or written notice.

Two mothers has removed children from state without permission or written consent. The father has had his license revoked because of failure to pay child support in the past, but when working was being deducted from pay check. He has no contact with one child as he doesn't know where he is now living. The other mother is not using his last name as court ordered. Is he still liable for child support and how can he get information to have the children returned back to the state and because of their actions can he get license reinstated since it has caused a number of arrest of driving without license to get to work.