Kaiser Wilhelm !! Was related to leaders of two of the nations he would engage in battle. Who are these leaders AND how were they related (Queen Victoria plays a role in this)?

Kaiser Wilhelm (Wilhelm II) was the last German Emperor and King of Prussia. He is particularly remembered for consolidating power in Germany, leading the country to become a world power. His reign began on June 1888, and lasted until his abdication in 1918, shortly after the end of World War I.

Wilhelm II was the eldest grandchild of Queen Victoria. He was first cousin of King George V of the United Kingdom and Nicholas II of Russia, as well as many other princes and princesses of the time.