Can I get my ex for childsupport if he is keeping my son from me and my daughter runs by my ex last name also?

You need to obtain advice from a family lawyer in your jurisdiction to get paternity established immediately for both kids as well as conservatorship, possession, rights and duties and child support.  Without court orders, you both have equal rights to possession of the children so your ex does not have to return your son.  It is possible in a paternity action to obtain back child support for your daughter. If your son is not in your possession, you need to ask for orders to adjudicate his parentage and obtain physical possession of him (through a court order).  Child support follows the possession. How long has he been with your ex? You need to file an action before you lose jurisdiction in your county to the county your ex resides in with your son as it will be more difficult and more expensive to file an action in a county where you have to travel a distance to the court. There are numerous issues with your case that need to be addressed as quickly as possible so please do not delay in seeking legal representation.