you will be asked one vital question - who is main driver?
If there is another driver on your policy s/he will probably be loaded as the main driver and deemed to be the main driver.
It is very dangerous to insure the second car in your name, if you are not the owner. This is often done to get cheaper insurance for a young erson with the policy in the older persons name.
In the event of a claim, insurers could repudiate liability and let you deal with claim yourself.