I don't believe @Critter-3 's answer applies to minor children.
I believe the general legal principle is that the domicile of a minor child is the domicile of the parents, or of the custodial parent if the parents are separated. See this:
https://domicile.uslegal.com/domicile-of-particular-persons/children/#:~:text=One%20acquires%20a%20d....
Some states, e.g. Georgia, address the issue directly:
https://law.justia.com/codes/georgia/2020/title-19/chapter-2/section-19-2-4/
From the Hawaii Tax Code:
"Domicile by operation of law" is assigned or attributed to an individual independently of the individual's residence or intention. In the usual case, domicile by operation of law is applied to those individuals, who, because of certain disabilities, are unable to acquire a domicile by choice. These would include such individuals as minor children and incompetents.
https://www.law.cornell.edu/regulations/hawaii/Haw-Code-R-SS-18-235-1.06
Also the Vermont Tax Bureau:
"The domicile of the custodial parent is the domicile of an unmarried minor, and
cannot be changed by the minor's own act."
I suspect a further Google search would turn up other examples.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
