Contemporary Scandinavian sources refer to Sten Sture…

Contemporary Scandinavian sources refer to Sten Sture as Sten Gustavsson or Herr Sten (Sir Sten); the practice of using noble family names as part of a personal name is not yet in use in Sweden at this time.

He was born around 1440, the son of Gustav Anundsson of the Sture family and Birgitta Stensdotter Bielke, half-sister of the future Charles VIII.

The Sture family is one of the high-ranking noble families of the time, though only distantly related to the royal house; his closest royal ancestor is King Sverker II of Sweden (both through family of Vinga and through family of Aspenäs).

Sture's father, Gustav Anundsson, had been Castellan of Kalmar Castle and a Privy Councilor, but died when Sten was four.

Birgitta Stensdotter remarried Gustav Karlsson of the Gumsehuvud family, and Sten had most likely been raised in their home, first at Kalmar Castle and later at Ekholmen Castle.

The fifteenth century in Sweden is largely defined by the political struggles and civil wars between the unionists of the Kalmar Union, seeking to unite Sweden with Denmark and Norway under the rule of the Danish monarchs, with Danish support, and the separatists seeking to reestablish Sweden as an independent kingdom under a rival Swedish monarch.

Due to his close family ties to the Swedish King Charles, the young Sten Sture had become part of the Swedish separatist political movement from an early age, and had visited Charles during his exile in Danzig.

He is mentioned as a knight in 1462 and as a privy councilor in 1466, and has taken up residence on the family estate at Räfsnäs north of Mariefred.

Sture had fought with Bishop and Regent Kettil Karlsson Vasa during the uprising against the Danish King Christian I in 1464, taking part in the decisive victory at Haraker.

He served as a military commander under King Charles VIII, defeating Erik Karlsson Vasa's uprising at Uppbo in 1470 and later in the same year successfully beating back Christian I's forces at Öresten.

He had married Ingeborg Tott, niece by marriage of Magdalen of Sweden, in 1467; she is a renaissance personality interested in theology and science and seems to have had some importance in the intellectual development during his reign.

The marriage is childless.

Sture's uncle, King Charles VIII, has named Sture heir to Charles' personal domains, and has left Sture in charge of the crown lands, including the city of Stockholm and Stockholm Castle.

On the death of Charles on May 15, 1470, Sture immediately becomes the most powerful noble and political force in the country.