His father was Birger Magnusson (Birger Jarl), Jarl of Sweden and de facto ruler of Sweden from 1250–66. His mother was Ingeborg of Sweden, daughter of King Eric X of Sweden and sister of King Eric XI of Sweden. 
In the conflict between his elder brothers, Valdemar and Magnus, he sided with Magnus. When Magnus had won and been proclaimed king in 1275, he made Erik, Duke of Småland. Erik died shortly thereafter and was buried at Varnhem Abbey together with his father and his father's second wife. 
When Birger Jarl's grave in Varnhem Abbey was opened and examined in May 2002, osteologist Torbjörn Ahlström from Lund University confirmed that the tomb contained the remains of three people – probably Birger Jarl, his second wife Matilda of Holstein, and Erik. His father's skeleton shows that he was about 172 cm long, while Erik was a few inches longer but with a much thinner build. His muscular attachments were poorly developed. In the vertebrae and sternum there were some signs of pathological changes.
|Ancestors of Eric Birgersson|
- J. Rosén. "Erik Birgersson". Svenskt biografiskt lexikon. Retrieved January 1, 2019.
- "Folkungaätten". Svenskt biografiskt lexikon. Retrieved August 1, 2020.
- Sten Engström. "Birger Magnusson". Svenskt biografiskt lexikon. Retrieved January 1, 2019.
- Sture Bolin. "Erik Knutsson". Svenskt biografiskt lexikon. Retrieved January 1, 2019.
- Sture Bolin. "Erik Eriksson". Svenskt biografiskt lexikon. Retrieved January 1, 2019.
- "Varnhem". varnhem.se. Archived from the original on June 16, 2008. Retrieved January 1, 2019.
- translated by Alexander Bugge (1914). "Magnus Haakonssøns saga in Norges Kongesagaer". Christiania: I. M. Stenersens Forlag. Retrieved January 1, 2019.
- "Skeletten från jarlen Birger Magnussons grav i Varnhems klosterkyrka. Osteologiska resultat och historiska konsekvenser baserade på undersökningen i maj 2002". Lund University. Retrieved August 1, 2020.
- Rolf Pipping, Kommentar till Erikskrönikan (Helsingfors 1926).
- Erik Birgersson, 1250–1275 Nordic Academic Press