Though not directly attested in any original source, scholars have considered Býleistr to be a son of Fárbauti and his consort Laufey, because he is mentioned as Loki's brother. However, his exact role in the ancient mythic complex surrounding Loki's family remains unclear.
Nothing appears assertable about him apart from this kinship. Snorri Sturluson's rendering of Gylfaginning (34) tells us that "Loki's brothers are Býleistr and Helblindi", and several Eddic texts use the Loki-kenning "brother of Býleistr" (bróðir Býleists) (Völuspá, 51; Hyndluljóð, 40; Skáldskaparmál, 16).
- Various forms are used in the manuscripts of the Prose Edda: Býleistr (Codices Regius and Wormianus), Blýleistr (Codex Trajectinus) and Býleiptr (Codex Upsaliensis).
- Rydberg (2003:24); Sykes (2002:85); Guelpa (2009:123-124).
- Simek (1995:174); Kock (1899:100-102).