His descendants claimed he was a son of the Norse god Odin. Snorri Sturluson identified him with the Norse god Baldur. Beldeg's mother's name is Frigg of the first three wives of Odin.

Anglo-Saxon Chronicle

A.D. 547. This year Ida began to reign, from whom arose the royal race of Northhumbria ; and he reigned twelve years, and built Bambrough, which was at first enclosed by a hedge, and afterwards by a wall. Ida was the son of Eoppa, Eoppa of Esa, Esa of Ingwi, Ingwi of Angenwit, Angenwit of Aloe, Aloe ot Benoc, Benoc of Brond, Brond of Beldeg, Beldeg of Woden, Woden of Frithowald, Frithowald of Frithuwulf, Frithuwulf of Finn, Finn of Godwulf, Godwulf of Geat (‘’Anglo-Saxon Chronicle’’ (A) : Cottonian Fragment (British Museum, Cotton MS. Otho B xi, 2); ‘’Anglo-Saxon Chronicle’’ (E) : The Laud (or "Peterborough") Chronicle (Bodleian, MS. Laud 636).

Canterbury manuscript

gives the ancestry of Ida, king of Mercia as Ida, son of Eoppa, son of Esa, son of Ingui, son of Angenwit, son of Aloc, son of Benoc, son of Brand, son of Beldeg, son of Woden (‘’Anglo-Saxon Chronicle’’ (F) : The Canterbury Bi-Lingual Epitome, British Library MS Cotton Domitian Aviii, ff.30-70).=

Winchester (or Parker) Chronicle

has Cynric, son of Cerdic, son of Elesa, son of Gewis, son of Wig, son of Freawine, son of Frithugar, son of Brand, son of Beldeg, son of Woden, son of Finn, son of Godwulf, son of Geats (‘’Anglo-Saxon Chronicle’’ (A) : The Winchester Manuscript, Cambridge, Corpus Christi College MS 173, ff.1-32).

Sources

• Cawley, Charles, “B. Kings of Bernicia, Kings of Northumbia 634-736, ‘’England, Anglo-Saxon, Danish Kings’’ at Medieval Lands: A prosopography of medieval European noble and royal families, visited May 6, 2018.
• The Anglo-Saxon Chronicle, trans. J. A. Giles (London, 1914), p.10.
• The Anglo-Saxon Chronicle, trans. Rev. James Ingram (London, 1823), with additional readings from the translation of Dr. J. A. Giles (London, 1847).
• Anglo-Saxon Bishops, Kings & Nobles, Eng. 104, p. 255.
• The Saga Library, F Ice. 1, "Heimskringla", v. 1, p. 16, v. 2, p. 148.
• The Viking Age, Gen. Hist. 19, v. 1, p. 28-68.