Really? I havent read a car insurance policy in a while but I could see it as being bases for not being covered. Also usually adding a driver is not a huge cost unless you have terrible driving history so it might just be worth it to avoid any headache.
Absolutely. My parents were basically told by their broker not to put the kids on the policies.
I did a little googling and found this:
(b) No misrepresentation shall avoid any contract of insurance or defeat recovery thereunder unless such misrepresentation was material. No misrepresentation shall be deemed material unless knowledge by the insurer of the facts misrepresented would have led to a refusal by the insurer to make such contract.
If you had added the kid when you purchased the policy, they would've issued the policy, albeit at a higher rate. Therefore, they can't void the policy retroactively (the part about issuing at a higher premium not qualifying for material misrepresentation comes from
here - search premium on the page to find the relevant portion).
Full disclosure: I actually found that bit in a thread from some law forum where the OP did have his claim denied and/or policy voided because of this type of issue, but the lawyers on the thread ended up pointing out that the insurer is not allowed to do that. No word in the thread of what ended up happening with the claim.