“She was, according to the same legends on which her own attestation is based, the daughter of Sune Sverkersson, one of the youngest sons of king Sverker I of Sweden. This semi-legendary knowledge provided her son Birger the ancestry in Sverker dynasty (the royal line which rivalled with Eric dynasty), which he used when elevating his son, who from Birger's wife's side descended from Eric dynasty, to the throne of Sweden as heir of both rival dynasties.”

Kilde: Wikipedia: http://en.wikipedia.org/wiki/Ingrid_Ylva