There’s a good chance that you’ll be paying more. Good thing is that you’ll be on that policy to negate his surcharges (meaning your discounts will at least lower the effects of his surcharges) and you’ll be getting a married discount. Also if either of you are under 25, you both automatically start getting the rates for people over that age. There’s a good chance that you won’t be paying TOO much more, but the best thing to do is just check.
You don’t want to do anything daft like.. exclude him. That would mean that if he had to use the vehicles, he’d be doing so illegally and wouldn’t be covered to drive those vehicles at all.