The short answer is 18. The child is legally an adult at age 18, and it is at that age that the child can say definitely who the child wants to live with. Until then, it is entirely in the discretion of the court to determine residency of a minor. Although the wishes of a child “of sufficient age” are entitled to considerable weight, these wishes are not controlling. “Sufficient age” is a very vague term. A lot is determined by the maturity of the child and the reasons of the child for wanting to live with one parent over another. There is case law suggesting a nine year old may be of sufficient age while a 17 year old may not. An attorney well-versed in custody matters should be consulted regarding the specific facts of your case.