In the Völsung cycle

Volsung Cycle

The Völsung Cycle is a series of legends in Norse mythology that were first recorded in medieval Iceland. The original Icelandic tales were greatly expanded with native Scandinavian folklore, including that of Helgi Hundingsbane, which, in turn, originally appears to have been a separate tradition...

, Sigi is the ancestor of the Völsung lineage. In the Völsunga saga

Volsunga saga

The Völsungasaga is a legendary saga, a late 13th century Icelandic prose rendition of the origin and decline of the Völsung clan . It is largely based on epic poetry...

(1), he is said to be one of the sons of Odin

Sons of Odin

Various gods and men appear as Sons of Odin or Sons of Wodan/Wotan or Sons of Woden in old Old Norse and Old High German and Old English texts.-Thor, Baldur, and Váli:...

. He is also listed among Odin's sons in the Nafnaþulur

Nafnaþulur

Nafnaþulur is a subsection of Snorri Sturluson's Prose Edda, the last part of the Skáldskaparmál. It is a listing in verse of names that may be used in poetry for various items, such as gods, giants, people, animals, and weapons...

. He had a son called Rerir

Rerir

In Völsunga saga, Rerir, the son of Sigi, succeeds his murdered father and avenges his death. He rules the Huns in Hunaland and becomes a powerful ruler. Rerir's son is Völsung....

.

He was outlawed for murdering a slave who had outdone him in hunting. With the help of Odin, Sigi fled from the land and led successful raids, so much so that he became king of Húnaland

Hunaland

Hunaland and its people are mentioned several times in the Poetic Edda, and in the Fornaldarsagas.Its origins are partly the old Frankish kingdom and partly in the Huns....

, a country name referring both to the territories of the Franks

Franks

The Franks were a confederation of Germanic tribes first attested in the third century AD as living north and east of the Lower Rhine River. From the third to fifth centuries some Franks raided Roman territory while other Franks joined the Roman troops in Gaul. Only the Salian Franks formed a...

, also known as the Hugones or Hugas, and the territories of the Huns

Huns

The Huns were a group of nomadic people who, appearing from east of the Volga River, migrated into Europe c. AD 370 and established the vast Hunnic Empire there. Since de Guignes linked them with the Xiongnu, who had been northern neighbours of China 300 years prior to the emergence of the Huns,...

. In his old age, he was killed by his wife's brothers who seized his kingdom. His son Rerir avenged him.

Sigi (or Siggi) is also mentioned in the prologue

Prologue (Prose Edda)

The Prologue is the first section of four books of the Prose Edda, and consists of a euhemerized Christian account of the origins of Norse mythology: the Norse gods are described as human Trojan warriors who left Troy after the fall of that city and settled in northern Europe, where they were...

 of the Prose Edda

Prose Edda

The Prose Edda, also known as the Younger Edda, Snorri's Edda or simply Edda, is an Icelandic collection of four sections interspersed with excerpts from earlier skaldic and Eddic poetry containing tales from Nordic mythology...

, where he is said to have ruled over Frakland (land of the Franks): "Odin's third son is named Sigi, his son Rerir. These the forefathers ruled over what is now called Frankland; and thence is descended the house known as Völsungs."