The court may appoint a guardian for an unmarried minor if all parental rights of custody have been terminated or suspended by circumstances or prior court order. A guardian appointed by will as provided in AS 13.26.121 whose appointment has not been prevented or nullified under AS 13.26.126 has priority over any guardian who may be appointed by the court but the court may proceed with an appointment upon a finding that the testamentary guardian has failed to accept the testamentary appointment within 30 days after notice of the guardianship proceeding.