Here's some more info-
We have a 23 yo daughter, who has not lived with us. I recently bought her a car to drive while she finishes college (2-1/2 years). I added her to my policy, against my better instinct, but my insurance agent agreed it was best economically.
We also have an Umbrella policy. We were told that JUST ADDING her to our policy AND if she has a moving violation on her record, our Umbrella would automatically double in premium cost. Fortunately the camera speeding ticket doesn't show up on her record, further proving my very opiniated voice that they are all about the money.
Anyway, I'm also told that if you do have an Umbrella and the kid causes an accident, the insurer generally cancels your Umbrella, especially if there is a major claim or 'other circumstances' are involved.
FWIW, I've had my own State Farm Auto Policy since I began driving at 17, when I bought my OWN car. Show me a kid today that has accomplished that.