Ultimately, you both will be held accountable for this accident. The insurance follows the vehicle, first. Now, if he drove the vehicle with your permission, he resides elsewhere, and he doesn't drive your vehicle with any kind of regularity, your insurance company should cover this accident to the limits of the applicable coverages for which you paid. (Your insurance company will probably investigate his physical address - since his mailing address is your physical address. But, if he resides elsewhere, that should be fine.) And, any insurance coverage he has will be "secondary" to your coverage.