HRH Charles's 15-Great Grandfather. Poss. Lady Diana's 17-Great Grandfather. HM Juan Carlos' 16-Great Grandfather. Philippe of Belgium's 16-Great Grandfather. Grand Duke Henri's 16-Great Grandfather. HM Margrethe II's 15-Great Grandfather. HM Beatrix's 15-Great Grandfather. HM Constantine II's 14-Great Grandfather. HM Carl XVI Gustaf's 14-Great Grandfather. HM Harald V's 15-Great Grandfather. Ksr Wilhelm II's 13-Great Grandfather.