Baldwin V of Jerusalem

Baldwin V (born 1177 or 1178; died 1186) reigned as the king of Jerusalem together with his uncle Baldwin IV from 1183 until his uncle's death in 1185, after which he was sole king until his own death in 1186. Baldwin IV's leprosy meant that he could not have children, and so he spent his reign grooming various relatives to succeed him. Finally his nephew was chosen, and Baldwin IV had him crowned as co-king in order to sideline the child's unpopular stepfather, Guy of Lusignan. When Baldwin IV died, Count Raymond III of Tripoli assumed government on behalf of the child king. Baldwin V died of unknown causes and was succeeded by his mother, Sibylla, who then made Guy king.

Source: Wikipedia — https://en.wikipedia.org/wiki/Baldwin_V_of_Jerusalem