Yes, the fact that your boyfriend's son lives at your residence could affect your insurance coverage that will extend to a claim for the damages you caused to his vehicle. Normally if you hit someone else's car they can make a claim through your property damage portion of your liability coverage but these may not be true in this case since you hit a car belonging to someone in your household.

The concept involved here is commonly referred to as a household exclusion. The mandatory liability coverage on your vehicles usually protects members of your household against claims brought by people who are NOT part of the household. If you have a provision in your auto insurance policy which excludes coverage for claims by all members of the insured’s (your) household then since the boyfriend's son is a part of the household it would appear he would not be able to place a claim against your policy for his damages.

From the information we have read, California is one state that upholds the validity of household exclusions in automobile policies. Section 11580.1 of the CA insurance code has been cited in reference to the household exclusion. To find out if you have this exclusion in your policy read it over and continue to discuss it with your insurance agent.

The California Department of Insurance may also be able to give you consumer help on this topic.