He was the eldest son of Frederick William George Adolph of Hesse-Kassel-Rumpenheim and his second wife Princess Anna of Prussia.

[2] His father died in 1884,[2] and he inherited the title of Landgrave which provided an allowance of £25,000 a year from the German government in addition to his extensive estates in Holstein and Hesse Castle.

[3] Frederick William III died on 14 October 1888 during a trip aboard the steamship Volga from Batavia to Singapore.

The only possible conclusion which could be come to was that, overcome by some sudden mental disturbance, to which his previous illness may have made him susceptible, his Royal Highness had, quite unconscious of what he was doing, gone through the port of his cabin, and had dropped into the sea.

Prince Frederick married Princess Margaret of Prussia, youngest sister of Kaiser Wilhelm II and a granddaughter of Queen Victoria of Great Britain.