You can petition the court for custody and/or visitation. Secondly, it is not your place to take your son to court for child support (unless you eventually win custody, which is a long shot at best) but rather the mother's or whoever has primary physical custody. You claim that "between him, your Dad and yourself, the baby wants for nothing." That sounds like your son is providing some degree of financial support. Has a support order been established? If so, then whatever agency in your state collects and enforces child support should be taking the necessary steps. If they're not, then whoever the obligee is (in all likelihood that would be the mother) has that option. The best you can do at this point is fight for your granddaughter to the fullest extent of the law in your state. A local attorney can provide you with firsthand advice.