16-year-old minor M¹ is disowned and forced from the house (into a raging thunderstorm) by asshat parent P¹. Other parent P² is absent, divorced from P¹ and living outside the country. M¹ flees to home of relative R¹, who takes M¹ in and assumes duties of guardianship.
How would R¹ go about assuming the legal status of guardian, and what might the legal consequences be for P¹'s asshattery?
*EDIT* Note that this is purely research for a work of fiction set in a contemporary or near-future USA. (sorry for that little omission.)