A child in Missouri cannot freely decide which parent she wants to live with until she is 18. If her mother has legal custody the father can find himself in legal trouble if he allows the child to move in with him without any court intervention unless the mother consents to the change. If there is child support involved, the issue is more complicated. However, the father can request a change in custody in the court that has jurisdiction. There is a good chance of success because in Missouri the judge will listen to a teen's request and take it into consideration in making the ruling.