Britain's Catherine, Duchess of Cambridge (C), Princess Stephanie (R), Hereditary Grand Duchess of Luxembourg, and Prince Guillaume (L), Hereditary Grand Duke of Luxembourg attend the Celebration of the 150th anniversary of the 1867 Treaty of London in Luxembourg on May 11, 2017. / AFP PHOTO / EMMANUEL DUNAND (Photo credit should read EMMANUEL DUNAND/AFP/Getty Images)
(From L) Princess Stephanie, Hereditary Grand Duchess of Luxembourg, Prince Guillaume, Hereditary Grand Duke of Luxembourg and Britain's Catherine, Duchess of Cambridge talk in Luxembourg city during the Celebration of the 150th anniversary of the 1867 Treaty of London in Luxembourg on May 11, 2017. / AFP PHOTO / JOHN THYS (Photo credit should read JOHN THYS/AFP via Getty Images)
Britain's Catherine, Duchess of Cambridge (3rdR), Grand Duke Henri of Luxembourg (3rdL), Grand Duchess Maria-Teresa of Luxembourg (2ndR), Prince Guillaume, Hereditary Grand Duke of Luxembourg (R), Princess Stephanie, Hereditary Grand Duchess of Luxembourg (2ndL) and Princess Alexandra of Luxembourg (L) pose for a photograph during the Celebration of the 150th anniversary of the 1867 Treaty of London in Luxembourg, on May 11, 2017. / AFP PHOTO / EMMANUEL DUNAND (Photo credit should read EMMANUEL DUNAND/AFP/Getty Images)
Britain's Catherine, Duchess of Cambridge (C), Prince Guillaume (R), Hereditary Grand Duke of Luxembourg, and Princess Stephanie (L), Hereditary Grand Duchess of Luxembourg, walk as they take part in the Celebration of the 150th anniversary of the 1867 Treaty of London in Luxembourg, on May 11, 2017. / AFP PHOTO / JOHN THYS (Photo credit should read JOHN THYS/AFP/Getty Images)
Britain's Catherine, Duchess of Cambridge (R), and Princess Stephanie, Hereditary Grand Duchess of Luxembourg, walk as they take part in the Celebration of the 150th anniversary of the 1867 Treaty of London in Luxembourg, on May 11, 2017. / AFP PHOTO / JOHN THYS (Photo credit should read JOHN THYS/AFP/Getty Images)
