Texas Family Code - FAM § 102.0031. Required Affidavit for Standing of Nonparent

(a) A nonparent who files or intervenes in a suit affecting the parent-child relationship in which another party to the suit is a parent of the child shall execute and serve with the nonparent's initial pleading an affidavit that:

(b) The court shall deny the relief sought and dismiss the suit or strike the intervention, as applicable, unless the court determines, based on the affidavit, that the affidavit contains facts adequate to support the allegation under Subsection (a)(1).