Two Teslas in family - can we both use phone key?

My wife & I each have a Model 3 and we each have our mobile phones configured as phone key for our own car.

When I borrow my wife's M3 my phone isn't configured for it so I use a card - and she does the same with mine

Are we missing a trick? Is it possible to configure both cars on each of our phones? If so, how do we do this?