All depends on the circumstances of the accident and the details of the son who was insured, and the car. If the son was in breach of his policy, the insurance company can sue him to recoup anything they paid out. Lots of reasons why that might be the case - not declaring mods, being a 'named driver' when he's actually the main driver etc. Can also happen in a road rage incident where the car was essentially used as a weapon.

You often hear people saying that the insurance companies won't pay out in the event of circumstances such as those above, but they are always obliged to pay out to third parties who are not at fault. They also always retain the right to get that money back off you. I know of similar happening where a lad spilt oil on the Nurburging causing a whole pile of damage - company paid out, then went after him for a 6 figure sum.