Question: Texas Subscriber
Answer: You should bill the mother because she brought the child to your facility. You aren't (and can't be) aware of the arrangements made between the parents and the courts for the child's care and payment of bills. It is up to the parents to sort that out among themselves if need be.
Bottom line: Whoever brings the child in for the visit is responsible to pay at the time, unless another arrangement has been made with the office beforehand. For example, if the parents are divorced and the father is the insurance subscriber and responsible for the children's medical bills, but the mother brings the child in for the visit, it should be determined before the office visit how copayments and coinsurance payments will be paid.