If your son is having child support taken out of his payroll check,then the mother has filed for child support. The law is that the mother can file at anytime for child support and get it, the burden of proof is upon the father. My guess is that you r son never married and never put his name on the birth certificate therefore leaving the birth certificate open to add a last name and that is more than likely what she did, you can put any name on the birth certificate. Had your sons name been on it she would not of been able to change it without going to court. What your son will have to do is have a parently test taken to prove that he is the father when the results come back he can take the mother to court and ask the court to change the babies last name to his. He will still have to pay child support,if there is any chance that he is not the father then he can't do anything,other then to have the child support dropped.

