Conrad IV, king of Germany (born 1228)

Conrad, a member of the Hohenstaufen dynasty, was the only son of Emperor Frederick II from his second marriage with Queen Isabella II of Jerusalem. He inherited the title of King of Jerusalem upon the death of his mother in childbirth. Appointed Duke of Swabia in 1235, his father had him elected King of Germany and crowned King of Italy in 1237. After the emperor was deposed and died in 1250, he ruled as King of Sicily until his death.

May 21 is the 141st day of the year in the Gregorian calendar; 224 days remain until the end of the year.