Typically an insurance company will require the policyholders to inform them of any licensed drivers within a household. So your parents will need to report to their insurance agent your licensing status, thus your junior license. The insurance company will then tell them if you need to be added to the policy at this time or when you get a full license.

As for driving your grandmother's car, she should inform her insurance company of your occasional or regular use of the vehicle to make sure that you will be covered while operating it. Insurance typically follows a vehicle first and driver second, so that is why it is important for her to check and make sure you would covered by her insurance for any accidents you may have while operating her vehicle.

The PA Department of Insurance states that a person can exclude a spouse or teenage driver. The DOI states that the FIRST NAMED insured may exclude any family member from the policy provided that the person being excluded can prove he or she has auto insurance with another company or the Assigned Risk Plan. So for your parents to exclude you from their policy it appears you would need to have your own insurance coverage with another auto insurance company.