We usually recommend that each person carries their own renter's insurance policy. This way, their contents are covered and they are provided liability coverage as well.
Renter's insurance only covers the named insured and resident relatives. This usually means the named insured’s spouse and/or children. Your specific renter's insurance policy will list who is considered a resident relative and how they would be covered on the policy.
Roommates, boyfriends, and girlfriends are different. They would not be covered on the policy unless they are listed as a second named insured. Some companies will allow a non-relative to be listed as a second named insured on a renter’s insurance policy, but not every company does. You would need to check with your agent to see what your company allows.
What is the risk of adding a roommate, boyfriend, or girlfriend as a 2nd named insured? Any claims that are filed under the policy go on your record too - even if you didn’t have anything to do with the claim. If your roommate/boyfriend/girlfriend files a claim, such as theft of property, this would go on your property insurance record as well and could affect your future insurance rates for up to 5 years.