Magnus IV of Sweden
His half-sister Ingeborg Ulfsdotter was in early 1350s married to a young nobleman, Benedict, Duke of Halland (c. 1330 – c. 1360). He was a favorite of King Magnus IV of Sweden. However the royal favorite was under increasing attacks and dissatisfaction from the party of high nobility. Benedict repudiated Duchess Ingeborg sometime in c. 1356. In 1360, Charles was with troops in Scania. Benedict was besieged at Rönneholm Castle ("Rönneholms slott"). Reportedly Charles personally took part in killing him.