King George V, Tsar Nicholas II, King Constantine I
King Louis XVI, King Oscar II
Emperor Franz Josef, King Edward VII
Emperor Wilhelm II, King Alfonso XIII
Answer
King Christian X of Denmark was born in 1870 and died in 1947. He was the grandson of Queen Victoria of the United Kingdom, and thus had many royal cousins, including King George V of the United Kingdom, Tsar Nicholas II of Russia, and King Constantine I of Greece.
The Reign of Christian X: Unveiling the Danish Monarch's Remarkable Legacy