Christian IX was King of Denmark from 1863 to 1906. From 1863 to 1864, he was concurrently Duke of Schleswig, Holstein and Lauenburg.
Growing up as a prince of Schleswig-Holstein-Sonderburg-Glücksburg, a junior branch of the House of Oldenburg which had ruled Denmark since 1448, Christian was originally not in the immediate line of succession to the Danish throne. However, in 1852, Christian was chosen as heir to the Danish monarchy in light of the expected extinction of the senior line of the House of Oldenburg. Upon the death of King Frederick VII of Denmark in 1863, Christian acceded to the throne as the first Danish monarch of the House of Glücksburg.
The beginning of his reign was marked by the Danish defeat in the Second Schleswig War and the subsequent loss of the duchies of Schleswig, Holstein and Lauenburg which made the king immensely unpopular. The following years of his reign were dominated by political disputes as Denmark had only become a constitutional monarchy in 1849 and the balance of power between the sovereign and parliament was still in dispute. In spite of his initial unpopularity and the many years of political strife, where the king was in conflict with large parts of the population, his popularity recovered towards the end of his reign, and he became a national icon due to the length of his reign and the high standards of personal morality with which he was identified.
Christian married his second cousin, Princess Louise of Hesse-Kassel, in 1842. Their six children married into other royal families across Europe, earning him the sobriquet "the father-in-law of Europe". Most current European monarchs are descended from him, including Queen Margrethe II of Denmark, Queen Elizabeth II of the United Kingdom, King Philippe of Belgium, King Harald V of Norway, King Felipe VI of Spain, and Grand Duke Henri of Luxembourg. The British consort Prince Philip, Duke of Edinburgh is also an agnatic descendant of Christian IX, as are Michael I of Romania and Constantine II of Greece, whose thrones have been abolished. Also, the queens consort Anne of Romania, Anne-Marie of Greece, and Queen Sofia of Spain are among his descendants.