Osbeorn Bulax

Under this year, the Anglo-Saxon Chronicle, recension D, related that: "At this time earl Siward went with a great army into Scotland, with both fleet and a land-force; and fought against the Scots, and put to flight the king Mac Bethad, and slew all that were best in the land, and brought thence much war-spoil, such as no man obtained before;   And there were slain his son Osbeorn, and his sister's son Siward, and some of his housecarls, and also of the king's, on the day of the Seven Sleepers (July 27)."

Siward therefore marched into Scotland and conquered the king battle ... "[10] Another legendary account, in the Vita et Passio Waldevi, a hagiography of Osbeorn's brother Waltheof, claimed that Osbeorn, called "Osbert Bulax", was killed by Northumbrians while his father was absent in Scotland.

[11] The accounts in Henry of Huntingdon and the Vita et Passio Waldevi are thought to be derived from a saga devoted to the life of Earl Siward.

[12] Geoffrey Gaimar's account related activity in 1053, an agreement made between Siward and Mac Bethad, but a death of Osbeorn is not mentioned.

When he died the following year, his only surviving son Waltheof (Osbeorn's brother) was underage and thus did not succeed immediately to the whole territory ruled by Siward, Northumbria going instead to Tostig Godwinson.