In the 11th century, English historian John of Worcester provided a pedigree for earl Beorn Estrithson that made his grandfather 'Spraclingus' a son of 'Ursius' (i.e. urso, Latin for bear or Bjørn in Danish, Björn in Swedish).
Two 13th-century writers relate folklore that derives Thorgil from the mating of a bear with a noblewoman. Danish historian Saxo Grammaticus recorded that the son born to such a union was 'named after his father' (i.e. called 'bear' - Ursius/Björn) and in turn became father of 'Thrugillus, called Sprageleg'. The Gesta Antecessorum Comitis Waldevi copies John of Worcester's pedigree but makes the Ursius, father of 'Spratlingus', an actual white bear.
In the 18th century, Danish historian Jakob Langebek suggested this bear story was allegorical, and that the brutish 'Wild' Björn, father of Thorgil, was a reference to Jomsviking brigand leader Styrbjörn the Strong (Styrbjörn Starke), depicted by sagas as the son of Olaf Björnsson, king of Sweden. Styrbjörn's wife in the sagas is stated to have been Tyra of Denmark, the daughter of Harold Bluetooth, king of Denmark and Norway. No primary source supports this royal ancestry for Thorgil, a connection almost impossible to maintain because of the chronological inconsistencies.
https://en.wikipedia.org/wiki/Styrbj%C3%B6rn_the_Strong
https://en.wikipedia.org/wiki/Styrbjarnar_%C3%BE%C3%A1ttr_Sv%C3%ADakappa
https://en.wikipedia.org/wiki/Thorgil_Sprakling

Gift med
Thyra Haraldsdottir.

Barn:
Torgils "Sprakalägg" Styrbjørnsson, född cirka 970, död 1027-09-22