Relative As an Insured?

Our insured's son has returned from Iraq and he will be stationed in Texas . The son, with his parents' permission, has rented a vehicle in his name in Maryland (where parents live) for twelve days. The son does not own a vehicle and does not have auto insurance.

Does the son have coverage under the parent's auto policy for liability and physical damage for the rental car? The parents have full coverage on their vehicles. The rental company did not call to verify coverage on the vehicle. Our insureds gave their policy information to the company.