We are doing a car loan for an individual and her son is co-borrower. The son and his wife are putting up their house as collateral for the loan. The mother also uses the house as her primary residence but does not have ownership in the house. The son and his wife will have have ROR, but will the mother also?

She doesn't have an ownership interest in the dwelling; therefore, she has no rescission right in the transaction. Son and wife, as you have said, do have rescission rights.

Depending on state law, mother may have homestead rights, and would need to sign recission. Check with your local attorney.