Texas Family Code - FAM § 156.101. Grounds for Modification of Order Establishing Conservatorship or Possession and Access

(a) The court may modify an order that provides for the appointment of a conservator of a child, that provides the terms and conditions of conservatorship, or that provides for the possession of or access to a child if modification would be in the best interest of the child and:

(b) Subsection (a)(3) does not apply to a conservator who has the exclusive right to designate the primary residence of the child and who has temporarily relinquished the primary care and possession of the child to another person during the conservator's military deployment, military mobilization, or temporary military duty, as those terms are defined by Section 153.701.