There is no liability coverage for the use of any vehicle, other than the named insured's covered auto, that is furnished or available for the regular use of any family member. So, if the son is renting a vehicle, that is a vehicle furnished for his regular use, and it is not included in the definition of the named insured's covered auto. The exclusion would prevent liability coverage for the son.

As for physical damage coverage, the auto policy does provide such coverage for nonowned autos, but in this case, the son would not have that either. Nonowned autos are defined as autos not owned by or furnished or available for the regular use of the named insured or any family member. If the son is renting a car, that is going to be available for his regular use, and that does not fit the definition of a nonowned auto.

If the rental is just a short-term rental, for example a weekend or even one week, that changes the dynamics and the exclusions are not going to apply. But, if the son is involved in long-term rentals, the parents' auto policy will not provide the insurance coverage he needs even though he is considered to be a family member.