(2) On an application for the purpose by an eligible person, the court may vary or discharge an order vesting the guardianship of a child in 1 parent or in any other person or persons. If the order is discharged, and no other order with respect to the guardianship of the child is made, guardianship vests in the person or persons (if any) who would be the guardian or guardians if the order discharged had not been made.
(3) In this section, eligible person, in relation to an order relating to a child, means any of the following persons: