DENMARK - MAY 18:  Celebration of Danish King CHRISTIAN X's 25 years of reign on May 18, 1937, at the castle of Christianburg in Copenhagen. For the occasion, the three royal families (of Denmark, Norway and Sweden) are photographed together after the banquet. First row : Princess INGRID of Denmark (2nd from left), King GUSTAVE of Sweden, Queen ALEXANDRINE of Denmark, King CHRISTIAN X of Denmark, King HAAKON of Norway and Princess INGEBORG of Denmark, the brother and sister of CHRISTIAN X.  (Photo by Keystone-France/Gamma-Keystone via Getty Images)