George V and Nicholas II were first cousins. Their mothers were sisters from Denmark. They famously looked alike.

Kaiser Wilhelm was a first cousin of Empress Alexandra, Nicholas' wife. He was Queen Victoria's first grandchild, son of her eldest daughter, Vicky.

Empress Alexandra was the daughter of Princess Alice, Queen Victoria's second daughter.

Kaiser Wilhelm and Tsar Nicholas were third cousins.

Kaiser Wilhelm II and Tsar Nicholas II were third cousins (both were great-great-grandsons of Paul I of Russia) as well as being second cousins once removed (both were descended from Frederick William III of Prussia) and the Kaiser was a first cousin of Nicholas's wife, Alix of Hesse.