Non-Paternal Father's Rights in Divorce

My question involves a child custody case from the State of: Texas.

I have a friend who is currently going through a rough divorce with a man who is NOT the biological father of her son. She attempted to keep it civil and they had an agreed upon schedule on when he would have her son. He as sense then done several things that worry her and leave his abilities as a father in question such as never bathing the boy, letting him wear the same clothes all weekend, not giving him his medication, and most recently he admitted to letting his son sleep in the bed with him and his girlfriend. Now that I got that out if my system..... she doesn't want him to have any rights. His name is handwritten on the birth certificate by her, he knows he's not the biological father, and there are paternity test results to prove it. What difficulties might she have in this case? P.s. the boy is 4

You are telling us, then, that the mother cheated on her husband some years back, that her husband was named by her as the father on the application for a birth certificate, that four years passed, that she's now divorcing her husband, and she has decided to bring up his non-paternity to try to keep him from having any custody or visitation rights?

Did either party raise the issue of nonpaternity in the divorce complaint or counter-complaint? Has it since been brought up in divorce proceedings?

When did the mother tell her husband that he's not the child's biological father? When were DNA tests performed, and why? Does the husband want to maintain his parental rights? What about the biological father - is he going to step in and be named as the child's father?

Negative, I'm sorry. She was pregnant from a previous relationship and then her and her husband got together and were married shortly after the child was born. He was aware that the child wasn't his own. They did the paternity test soon after childbirth to have it on record. He also knows that his name is on the birth certificate.