He was born the son of Magnus Anundsson Sture and Karin Algotsdotter, daughter of Algot Magnusson who belonged to the ancient Västergötland dynasty of justiciars.
[citation needed] Through his marriage with Märta Bosdotter of Rigshult, Algot received new positions and moved from Västergötland to the east-coast regions of Sweden: Östergötland and the provinces around the Lake Mälaren.
[4] In 1392–1393 Algot was castellan of Örebro, and the winter 1393–1394 he held power in all Uppland and led the siege of Stockholm, the principal town yet in hands of the deposed King Albert's representatives.
Algot played a key role in the lengthy peace negotiations in Lindholmen and Helsingborg, which ended with the release of Albert, in exchange for his pledge to pay a large sum in compensation to Queen Margaret, or to give up Stockholm within three years.
[5] Around 30 August 1381 Algot married Märta Bosdotter of Ringshult, scion of an important Östgöta family and widow of castellan Christopher Mikelsdorp.
Her father was lord Bo Bosson of Ringshult, and her grandmother had been Cecilia Knutsdotter of Aspanes, descendant of several dukes.