https://en.wikipedia.org/wiki/Prince_Christoph_of_Hesse
"Prince Christoph Ernst August of Hesse (14 May 1901 – 7 October 1943) was a nephew of Kaiser Wilhelm II. He was a German SS officer and was killed on active duty in a plane crash during World War II. His brother-in-law, Prince Philip of Greece and Denmark, fought on the British side and married the future Queen Elizabeth II after the war."
"His father, Frederick Charles, a scion of the House of Hesse, was elected King of Finland in 1918, when Finland declared its independence after the collapse of the Russian Empire.[2] However, the overwhelming Republican victories in the 1919 Finnish parliamentary election effectively ended any ambitions for a Finnish monarchy."