In these cases you mentioned, the mortgagee (lender) only recognizes bad luck! This mortgage is invalid: first, the property right of the house is unknown, the owner of the real estate license no longer exists (dead), and the inheritance procedures have not been handled, so it cannot be mortgaged; Second, the person who can inherit the house did not agree to the mortgage statement in writing (this has nothing to do with knowing); Third, more importantly, there is no real estate mortgage registration.

C can ask for the return of the real estate license, but in this case, because A and B are suspected of fraud, they can be included in criminal responsibility and can be handled by the procuratorate and public security organs. This property right certificate is one of the exhibits and cannot be returned to C now; As for whether D is an accessory, it is up to the administrative organ and the court to judge!