HRH Charles's 11-Great Grandmother. HM Juan Carlos' 11-Great Grandmother. Philippe of Belgium's 12-Great Grandmother. Grand Duke Henri's 12-Great Grandmother. HM Margrethe II's 11-Great Grandmother. HM Beatrix's 10-Great Grandmother. HM Constantine II's 11-Great Grandmother. HM Carl XVI Gustaf's 12-Great Grandmother. HM Harald V's 11-Great Grandmother. Ksr Wilhelm II's 9-Great Grandmother. Boris Johnson's 12-Great Grandmother.