HRH Charles's 17-Great Aunt. Lady Diana's 18-Great Aunt. HM Juan Carlos' 17-Great Aunt. Philippe of Belgium's 18-Great Aunt. Grand Duke Henri's 18-Great Aunt. HM Margrethe II's 15-Great Grandmother. HM Beatrix's 14-Great Grandmother. Otto von Bismarck's 10-Great Aunt. HRH Catharina-Amalia's 13-Great Grandmother.