Do I have to be an owner of co-owner of the second car to add it to my existing policy?
It all depends on the company. Some companies don't care who is on the title, others will only write a policy in the names that are on the title and others will add it to the existing policy so long as one of the names on the title is also one of the named insureds on the policy.
You really have to contact your agent to see what the companies rules are.
My husband just added my car to his insurance policy and he is not the owner or the co-owner, so I believe it can be done.
Answers:
Realistacally you need to have an insurable interest before you are suppose to be able to insure a vehicle. Doesn't mean the policy won't get written. If people weren't the owners or didn't have an insurable interest then they would all just group together to get cheaper rates. I would just combine with my friends and family for 1 big policy.
The named insured, or spouse, should have ownership interest in all vehicles listed on their policy.
Otherwise an insurance company would have to determine if there is any "insurable interest" at the time of claim - and if there isn't, they don't have to pay.
That means, you can't insure your buddy's car, if you EXPECT payment at the time of loss.
I live in California and my daughters car is on my insurance and my name is not on the car.