Nothing is known about him apart from this kinship. Snorri Sturluson states in his Gylfaginning (34) 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).
Though not directly attested in any original source, scholars have considered Býleistr to be a son of Fárbauti and his consort Laufey, because they are mentioned as Loki's brothers. However, their exact role in the ancient mythic complex surrounding Loki's family remains unclear.
- 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).