According to Ragnar Lothbrok's saga, while Sigurd was just a boy, his half-brothers Eric and Agnar were killed by Swedish king Eysteinn Beli (also known as Östen).

When Áslaug heard the news of Eric and Agnar's death, even though she was not their mother, she cried blood and asked the other sons of Ragnar to avenge their dead brothers.

Because the Swedish king controlled Uppsala and a holy cow named Sibilja, Ivar the Boneless believed gods were on Eysteinn's side and feared the magic that ruled there.

[3] The Danish historian Saxo Grammaticus relates that Sigurd, as a young man, was close to his father and sojourned for a time in Scotland and the Scottish Islands.

Sigurd's brother, Ivar the Boneless, devised a strategy in which the Great Heathen Army occupied and sacked York, to provoke Ælla into engaging on the Vikings' terms.

[6][7][8] Ragnarssona þáttr states that when his father died, Sigurd inherited Zealand, Scania, Halland, the Danish islands, and Viken.

A Danish Viking king called Sigfred, who appears to have become landless by this time, was killed in West Francia in 887; he is quite possibly the same person.

[11] Helge may have briefly succeeded his purported father-in-law as king of Denmark before being overthrown by Olof, a Viking chief who swept down from Sweden in about the year 900.

Hardegon or Harthacanute succeeded Sigtrygg Gnupasson as the king of part of Denmark (probably Jutland, but according to later tradition Zealand, Scania and Halland) in about 916.

Gorm's son, Harald Bluetooth succeeded his father as king and married possibly three times with Gunhild, Tove and Gyrid.