Generally, the question of guardianship arises between the parents themselves. In certain cases, the dispute may be between one (or both) of the parents and another person other than the mother or father who is called a “Third Party”. Letting the child under such third party’s custody is called third party guardianship. Best interest of the child will be primary criteria for granting such custody. Nonparental custody can be temporary or permanent. It allows the person taking care of the child to make legal and medical decisions on behalf of the child.

In Washington any person other than a parent can commence the child custody proceeding if the child is not in the physical custody of one of its parents or if the petitioner alleges that neither parent is a suitable custodian.