Christian IX was the King of Denmark from 1863 until his death in 1906. He was born on April 8, 1818, and is often referred to as the "Father-in-law of Europe" due to his children's marriages into various royal families. His reign saw significant political changes, including the introduction of a new constitution in 1866. During his time as king, Christian IX worked to strengthen Denmark's position in Europe. He faced challenges such as the Second Schleswig War in 1864, which resulted in the loss of territories. Despite these difficulties, he is remembered for his efforts to modernize the Danish monarchy and promote national unity.