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, which strengthened diplomatic ties across the continent. His reign saw significant political changes, including the rise of constitutional monarchy in Denmark. During his rule, Christian IX faced challenges such as the Second Schleswig War, which resulted in the loss of territories to Prussia. He ruled until his death on January 29, 1906, leaving a legacy of increased stability and modernization in Denmark.