Haakon was the younger son of Magnus Eriksson, king of both Norway and Sweden. His older brother Eric was meant to succeed their father on the throne of Sweden, while Haakon was made king of Norway in his father's lifetime. Magnus greatly favored Haakon over Eric, leading to the latter's rebellion and seizure of Southern Sweden. Eric died in 1359, and Haakon became co-ruler of Sweden with his father three years later. The two reigned over Sweden together until 1364, when they were deposed in favor of Magnus' sororal nephew, Albert of Mecklenburg, by a clique of exiled Swedish noblemen led by Bo Jonsson Grip. Magnus and Haakon tried to retake the Swedish throne, but without success.