Legal Question in Family Law in Texas

I assume that there are no court orders in place.

To get your son back: file for divorce, ask for temporary orders, and get your wife served with citation wherever she is.

As things stand, there's not much you can do--she has just as much a right to have the kids with her as you do. The only way to change that is by having a court lay out when you and she will have the kids, along with various other things like who gets to pick where they live, deal with schools and doctors, pay support, and so on. You can get that accomplished either with or without filing for divorce, so if you don't want a divorce right now, you'd just file what's called a SAPCR ("Suit Affecting Parent-Child Relationship") suit in the family court of the county where you live, assuming it's been less than six months since she moved out (if it's longer than that, you'd do the same thing, but file in whatever county the kids are in). You can also ask that the court put in place temporary orders that would at least let you see the kids while the case is pending. Good luck.