Good afternoon Gerald,
I'm Doug, and I'm very sorry to hear of your situation. My goal is to provide you with excellent service today.
While I am sure from the position of most men in your position it ought to be illegal, there is nothing inherently unlawful in the state if Texas about an estranged wife, in the middle of a divorce or otherwise, choosing to live with another man and allow that person to babysit her child(ren).
If there is something seriously wrong with this situation such as the boyfriend is a convicted child sex offender, while you could not prevent her from living with the guy, you would have grounds to seek full custody of your children.
But absent something unusual about the situation, not what you describe is not a violation of law in Texas---or any other state for that matter.
You may reply back to me using the Reply link and I will be happy to continue to assist you until I am able to address your concerns, to your satisfaction.
Please be so kind as to rate my service to you. That is the only way I am credited for assisting you.
I wish you and yours the best in 2016,