Christian IX of Denmark sibling Prince Julius of Schleswig-Holstein-Sonderburg-Glücksburg
The Danish succession crisis
In the 1840s, it became increasingly clear that the Danish monarchy was facing a succession crisis. When King Christian VIII succeeded his first cousin King Frederick VI in 1839, the elder male line of the House of Oldenburg was obviously on the point of extinction, as the king's only son and heir-apparent Crown Prince Frederick seemed incapable of fathering children and the king's only brother Prince Ferdinand's marriage to King Frederick VI's daughter was childless. King Frederick VII's childlessness presented a thorny dilemma and the question of succession to the Danish throne proved complex, as the rules of succession in the different parts of the Danish monarchy united under the king's rule, the Kingdom of Denmark proper and the three duchies of Schleswig, Holstein and Saxe-Lauenburg, not being the same, the possibility of a separation of the crown of Denmark from its duchies became probable.
brother or sister kin