How to Get Custody or Guardianship of My Little Brother

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

I'm 25 years old, and married. My younger brother is 13. My mother and I have talked and we both think it would be nice to have my brother come stay with my husband and I for a school year (or more, if my brother wants). She is struggling financially and it would be nice for her to be able to focus on work and get back on her feet financially. His father, however, would most likely take issue, if only because I live in a different city and it could affect his visitation.

My brother doesn't even want visitation at all with is father and wants to go before a judge to tell them so. (Hes 15k behind on child support and an abusive alcoholic.) My brother wants to give a school year with us a try (mainly to see if he likes the school. It has an educational track for kids in high school that want to work with computers and programming, etc, which my brother has expressed interest in.)

Would he be able to prevent my brother from coming to staying with us, and my mother granting me guardianship for that time period, or how would that work?

If mom doesn't want to maintain custody, dad gets first shot. If you want to try to overrule dad's rights as the child's parent, I suggest that you retain a lawyer to assist you - even if he's an "abusive alcoholic" you should not expect that it is going to be easy.