Auto insurance eligibility and pricing are tied to loss potential. Insurers look at numerous factors to evaluate risk, and this includes driving records for all household members.
A housemate with a poor driving record affects your auto insurance options. Your premium may go up, or the insurer may decide to discontinue coverage. It might be time to shop for another carrier or search for a company willing to exclude the problematic driver. A driver exclusion means no insurance protection for the excluded individual.
Be up front with your insurer about all household members. Not disclosing this information could jeopardize coverage if a crash occurs.