(1) By mutual consent, the parents of a child may modify an agreement regarding custodial responsibility made in accordance with this part.
(2) If an agreement is modified under Subsection (1) before deployment of a deploying parent, the modification shall be in writing and signed by both parents and any nonparent who will exercise custodial responsibility under the modified agreement.
(3) If an agreement is modified under Subsection (1) during deployment of a deployed parent, the modification shall be agreed to in a record by both parents and any nonparent who will exercise custodial responsibility under the modified agreement.