Under what conditions is custody (Hadanah) established?

Primary text

Custody is established only for a child or an insane person (ma'tuh). Custody is not established over a physically capable, mature, sane individual; such an individual has the free choice to reside with whomever they wish between their parents. If the child is a male, he is permitted to be alone, as he is self-sufficient from his parents, although it is recommended he not isolate himself from them and maintain his righteousness toward them.