I would presume the child is a resident of the state where they actually reside and not the military residency status of their parents which can be legally different due to the Military options available.
So the father could have SLR as OH and the mother still uses an old state because of MRSSA say FL but they all live in PA then the child is a resident of PA for income tax purposes. They don't get to choose one of the parent's options because they are not the military member or the spouse.
