During World War I, which nation's monarchs were blood related?

The story behind the answer

England, Germany, and Russia are correct because their World War I monarchs were close relatives. King George V (Britain/England) and Kaiser Wilhelm II (Germany) were first cousins, both grandchildren of Queen Victoria. George V and Tsar Nicholas II (Russia) were also first cousins through their mothers, sisters who were daughters of Denmark’s King Christian IX. Wilhelm II and Nicholas II were more distant cousins via shared royal ancestors, and Nicholas’s wife, Alexandra, was Queen Victoria’s granddaughter.

This “war of the cousins” shows how intertwined Europe’s royal houses were—yet family ties couldn’t stop geopolitical rivalries. To remember: think “E–G–R” (England–Germany–Russia) and “Victoria + Christian IX = Europe’s family feud.” The famous “Willy–Nicky” telegrams between the Kaiser and the Tsar even used their cousinly nicknames.