Erik Magnusson, King of Sweden

Erik Magnusson (1339 – 20 June 1359), sometimes known as Erik XII, was a Swedish prince who was formally elected King of Sweden in 1344. He held no real power before 1356, when he led a rebellion against his father, King Magnus Eriksson, forcing Magnus to divide the kingdom with him. Erik then ruled large parts of Sweden and Scania alongside his father until his sudden death in 1359, possibly from the Black Death.

Source: Wikipedia — https://en.wikipedia.org/wiki/Erik_Magnusson,_King_of_Sweden