During WW1, the King of England, the Tsar of Russia, and the Emperor of Germany were all first cousins.
Nicholas II or Nikolai II Alexandrovich Romanov, known in the Russian Orthodox Church as Saint Nicholas the Passion-Bearer, was the last Emperor of Russia, ruling from 1 November 1894 until his forced abdication on 15 March 1917. His reign saw the fall of the Russian Empire from one of the foremost great powers of the world to economic and military collapse.
His memory was reviled by Soviet historians as a weak and incompetent leader whose decisions led to military defeats and the deaths of millions of his subjects. By contrast Anglo-Russian historian Nikolai Tolstoy, leader of the International Monarchist League, says, "There were many bad things about the tsar's regime, but he inherited an autocracy and his acts are now being seen in perspective and in comparison to the terrible crimes committed by the Soviets."
Nicholas was related to several monarchs in Europe. His mother's siblings included Kings Frederick VIII of Denmark and George I of Greece, as well as the United Kingdom's Queen Alexandra (consort of King Edward VII). Nicholas, his wife Alexandra, and German Emperor Wilhelm II were all first cousins of King George V of the United Kingdom. Nicholas was also a first cousin of both King Haakon VII and Queen Maud of Norway, as well as King Christian X of Denmark and King Constantine I of Greece. Nicholas and Wilhelm II were in turn second cousins-once-removed, as each descended from King Frederick William III of Prussia, as well as third cousins, as they were both great-great-grandsons of Tsar Paul I of Russia.
In addition to being second cousins through descent from Louis II, Grand Duke of Hesse and his wife Princess Wilhelmine of Baden, Nicholas and Alexandra were also third cousins-once-removed, as they were both descendants of King Frederick William II of Prussia.
Tsar Nicholas II was the first cousin-once-removed of Grand Duke Nicholas Nikolaevich. To distinguish between them the Grand Duke was often known within the imperial family as "Nikolasha" and "Nicholas the Tall", while the Tsar was "Nicholas the Short".
In his childhood, Nicholas, his parents and siblings made annual visits to the Danish royal palaces of Fredensborg and Bernstorff to visit his grandparents, the king and queen. The visits also served as family reunions, as his mother's siblings would also come from the United Kingdom, Germany and Greece with their respective families. It was there in 1883, that he had a flirtation with one of his English first cousins, Princess Victoria. In 1873, Nicholas also accompanied his parents and younger brother, two-year-old George, on a two-month, semi-official visit to England. In London, Nicholas and his family stayed at Marlborough House, as guests of his "Uncle Bertie" and "Aunt Alix", the Prince and Princess of Wales, where he was spoiled by his uncle.