i just went through this... i moved from NJ to PA with my 2 year old son.
i looked it up for Texas, & could not find anything specific to your state, but i can tell you what i had to prove in court:
The relative strength, nature, quality, extent of involvement and stability of the child's relationship with each parent, siblings, and other significant people (such as grandparents) in the child's life
Whether disrupting the contact between the child and the person with whom the child resides a majority of the time would be more detrimental to the child than disrupting contact between the child and the person objecting to the relocation
The intent of each person for seeking or opposing the relocation, and the good faith of each of the parties in requesting or opposing the relocation
The quality of life, resources and opportunities available to the child and to the relocating party in the current and proposed geographic locations
The feasibility of alternative arrangements to foster and continue the child's relationship with and access to the other parent, considering finances and practical concerns
* The financial impact and logistics of the relocation or its prevention
basically, my son's father had to prove to the judge that my reasons were not stupid or silly. i had to prove that the move was the best interest of the child, NOT myself, obviously.