Poss. HM George I's 15-Great Grandmother. Poss. HRE Charles VI's 14-Great Grandmother. Poss. U.S. President [T. ROOSEVELT]'s 21-Great Grandmother. Poss. PM Churchill's 23-Great Grandmother. Poss. Lady Diana's 23-Great Grandmother. Poss. PM Cameron's 25-Great Grandmother.