Texas Family Code - FAM § 101.024. Parent

(a) “Parent” means the mother, a man presumed to be the father, a man legally determined to be the father, a man who has been adjudicated to be the father by a court of competent jurisdiction, a man who has acknowledged his paternity under applicable law, or an adoptive mother or father.  Except as provided by Subsection (b), the term does not include a parent as to whom the parent-child relationship has been terminated.

(b) For purposes of establishing, determining the terms of, modifying, or enforcing an order, a reference in this title to a parent includes a person ordered to pay child support under Section 154.001(a-1) or to provide medical support or dental support for a child.