Christian IX of Denmark was born on April 8, 1818, and became the King of Denmark in 1863. He was known as the "Father-in-law of Europe" due to his children's marriages into various royal families across the continent. His reign lasted until his death in 1906, making him one of the longest-serving monarchs in Danish history. During his time as king, Christian IX faced significant challenges, including the loss of the duchies of Schleswig and Holstein to Prussia in the Second Schleswig War. Despite these difficulties, he worked to modernize Denmark and strengthen its position in Europe, promoting peace and stability.