Conrad IV of Germany

Conrad IV (1228–1254), the only son of Emperor Frederick II and Isabella II of Jerusalem, inherited Jerusalem when his mother died giving him birth. Made Duke of Swabia in 1235, he was elected King of the Romans in 1237.

He fought Pope Innocent IV and rival kings, and after Frederick's death in 1250 ruled Sicily and seized Naples in 1253. Excommunicated in 1254, he died of malaria at Lavello on 21 May, leaving his son Conradin; his death opened the Interregnum.