Prince Frederick of Hesse (May 1, 1868 - May 28, 1940), Friedrich Karl Ludwig Konstantin, Prinz und Landgraf von Hessen und Brabant, brother-in-law to Emperor Wilhelm II of Germany and elected king of Finland (October 9, 1918). ...
The elder Frederick, a Danish military officer, had been one (and perhaps the foremost) of the candidates of Christian VIII of Denmark in the 1840s to succeed on the Danish throne if the latter's male line died out, but renounced his rights to the throne in 1851 in favor of his sister, Louise.
On January 25, 1893, Frederick married Princess Margaret of Prussia, the youngest daughter of the late Frederick III, German Emperor and Victoria, Princess Royal, eldest daughter of Victoria of the United Kingdom and her consort Albert of Saxe-Coburg and Gotha.
Landgrave Alexander of Hesse abdicated as the head of the House of Hesse on March 15, 1925, and was succeeded by Frederick.
Louise of Hesse (born 7 September 1817 at Kassel, died 29 September 1898 at Bernstorff) was a German noblewoman and (from November 15, 1863) the Queen Consort to King Christian IX of Denmark.
Louise's paternal grandparents were Prince Frederick of Hesse, youngest brother of William I, Elector of Hesse, and Princess Caroline of Nassau-Usingen; and her maternal grandparents were Sophie Frederikke of Mecklenburg-Schwerin and Hereditary Prince Frederick of Denmark and Norway, sometime Regent of Denmark and Norway, youngest son of King Frederick V of Denmark.
Her nephew FrederickCharles of Hesse, married to a granddaughter of Queen Victoria and of German emperor Wilhelm I, became 1918 elected as King Charles of Finland.