Grandparents, stepparents and other third party caregivers have many different options regarding the care of a child if the parent agrees to the custody change.
Changes in custody are sometimes needed to allow the third party to enroll the child in school, get access to medical records and more.
If the parent agrees, a 
Delegation of Parental Authority Form can provide a caregiver limited authority.
If parent doesn’t agree
If the parent doesn’t agree to a custody change, you will need to file a motion to have the court decide. There is not a pre-made form for third party custody. The Law Library has materials and samples on this topic. If additional assistance is needed, you may want to make an appointment for the Family Self Help Clinic.
For more information