Legal Question in Real Estate Law in California

Cars are personal property, not "real estate" or "real property."

Your husband is the one with the right of possession. You probably have no greater right to the car than the unspecified family member who has it now.

Is your husband interested in getting the car back? If so, I'd suggest that he contact a licensed repossession service who can do the job skillfilly and legally.

If you have some claim to rightful possession based on, for example, it being community property, or the registration and title are wrong due to fraud, forgery, etc., you could perhaps sue the alleged wrongdoers and get a court to grant you possession and/or title.

Otherwise, it seems to me it's your husband's call.