Tex. Fam. Code §153.002
Best Interest Of Child; Rebuttable Presumption In Suit Between Parent And Nonparent

The best interest of the child shall always be the primary consideration of the court in determining the issues of conservatorship and possession of and access to the child.

In a suit between a parent and a nonparent, it is a rebuttable presumption that: (1) a parent acts in the best interest of the parent's child; and (2) it is in the best interest of a child to be in the care, custody, and control of a parent.

In a suit between a parent and a nonparent, the nonparent may overcome the presumption under Subsection (b) by proving by clear and convincing evidence that denial of the relief requested by the nonparent would significantly impair the child's physical health or emotional development. If the court renders an order in the suit granting relief to the nonparent, the court shall state in the order: (1) the specific facts that support the court's finding that denying the relief requested by the nonparent would significantly impair the child's physical health or emotional development; and (2) the extent to which the nonparent has overcome the presumption under Subsection (b).