Poss. HM George I's 12-Great Aunt. Poss. HRE Charles VI's 13-Great Aunt. HRH Charles's 18-Great Grandmother. Poss. Lady Diana's 21-Great Aunt. PM Cameron's 18-Great Aunt. HM Juan Carlos' 17-Great Grandmother. Philippe of Belgium's 17-Great Grandmother. HM Manuel II's 16-Great Grandmother. Ksr Wilhelm II's 15-Great Grandmother.