Legal Question in Family Law in Texas

You'll need to file what's called a "SAPCR" ("Suit Affecting Parent-Chikd Relationship") asking for custody and ask the court to grant temporary orders giving you custody while the case is pending. If the situation is what I think you're saying it is, you're pretty sure you're the biological father, but probably you weren't named on the birth certificate and there's been no Acknowledgement of Paternity signed (I think you're saying you didn't know your son existed until he showed up on your doorstep one day).

If that's all the case, things may be a bit messy due to the fact that the mom was either married to someone else when your son was born, or certainly married him pretty soon thereafter. That means that there is a legal presumption that her husband is your baby's father, and to get anywhere with this, you'll have to defeat that presumption. That means you'll probably also have to request that the court adjudicate parentage (decide who the real father is), which requires that DNA testing be done.

I think you have a good case--judges do not like hearing stories about people abandoning babies and then trying to get them back to collect benefits. But your situation is complicated, and I've heard stories like this from a lot of people who tried to handle custody cases themselves and were shocked when they lost, because factually, they were in good shape. Unfortunately, the procedural end of all this is not going to be easy to deal with, and honestly I don't think most people in your position could handle it themselves. There's a lot to screw up, and chances are you wouldn't even know the issues you were screwing up even existed until it was too late. So, please get an attorney--it will be worth it. Good luck.