[6] Birger, likely born around the time of the Battle of Gestilren in 1210, spent his childhood and adolescence in Bjälbo, Östergötland.

[7] However, since his father, Magnus Minnesköld, is believed to have died no later than 1210, Birger's birth may have occurred a few years earlier.

[8] Birger's mother Ingrid Ylva was, according to Olaus Petri, a daughter of Sune Sik and the granddaughter of King Sverker I of Sweden.

[citation needed] According to some 15th and 16th century sources, Birger was responsible for a military campaign against the Novgorod Republic in 1240, which ended in a victory by Alexander Nevsky during what is known as the Battle of the Neva.

[10] However, the original 14th-century Russian record of the battle gives no information on this at all,[11] and the first sources that link Birger Jarl to the Neva campaign date from mid-15th century.

[12] When the papal diplomat William of Modena visited present Sweden around 1248, he urged the Swedish kings to fulfill the rules of the Catholic Church, an exhortation which Birger seems to have taken as a chance to strengthen his position by simply taking the side of the church against other members of his family (alternatively it's possible to interpret this as a manifestation of his pious side).

[16] In 1252, a year after another victory over the folkungs at the Battle of Herrevadsbro [sv], Birger wrote two carefully dated letters, the first mention of Stockholm interpreted as the foundation of the city or at least some sort of special interest in the location.

Neither of the letters give a description of the location, however, and while archaeological traces of older defensive structures have been found there, what did exist on the premises before the mid-13th century remains debated.

It has been suggested Birger chose the location for several reasons: Partly to curb domestic magnates by isolating them with a "lock of Lake Mälaren", offering a defense to the lands around Mälaren from invading enemies in the process; and to create a commercial bridgehead to attract German merchants.

While Birger's direct involvement in the foundation of the city remains speculative, it probably was no accident it was founded on the location at this time.

The marriage was contracted relatively near the time when Ingeborg's brother, the once-deposed Erik Eriksson, returned from exile in Denmark in 1234.