Germany. Kaiser Wilhelm I (1797-1888) was a Hohenzollern king of Prussia. During his reign Germany was unified into one nation. A younger son, Wilhelm was not expected to become king and had a career in the military. Wilhelm became king in 1861 when his older brother, King Frederick Wilhelm IV, died childless. Wilhelm's wife was Princess Augusta of Saxe-Weimar-Eisenach. They had two children.