As told in the surviving epic poem, Beowulf was the son of Ecgþeow, a warrior of the Swedish Wægmundings. Ecgþeow had slain Heaðolaf, a man from another clan (named the Wulfings) (according to Scandinavian sources, they were the ruling dynasty of the Geatish petty kingdom of Östergötland).

On his father’s side, Beowulf belonged to a lineage, known as the Wægundings, a noble house of warriors. His father was named Ecgtheow. His young kinsman, perhaps nephew or great nephew, Wiglaf, also belonged to this line.

Beowulf gives Hygelac 's genealogy: according to the poem, he was the son of Hrethel and had two brothers Herebeald and Hæþcyn, as well as an unnamed sister who was married to Ecgtheow and was the mother of the hero Beowulf. Hygelac was married to Hygd, and they had a son Heardred and an unnamed daughter who married Eofor.