Frederick VII of Denmark
In November 1863, Frederick of Augustenborg claimed the twin-duchies in succession to Frederick VII of Denmark, who also was the last king of Denmark who, by primogeniture, was also sovereign Duke of Schleswig and Holstein, but whose death extinguished the patriline of Denmark's hereditary Oldenburg kings. The resulting divergence of hereditary claims to the duchies eventually developed into the Second War of Schleswig.