http://en.wikipedia.org/wiki/Siward,_Earl_of_Northumbria

Sigurd Björnsson, also known as Siward the Dane , was an English nobleman in the eleventh century, and the earl of Northumbria.
Siward was allegedly a descendant of the Danish royal family, whose ancestors may have arrived in England a few generations earlier as part of the Norse colonisation of Britain. Some historians suggest that Siward arrived in England with King Canute I and that Canute invested the title and position of Earl of York onto him in 1031.
In 1033 Siward married into the Northumbrian princely house, that of Bamburgh by taking Aelfled, granddaughter of Uchtred, former Earl of Northumbria, as his wife and thus strengthening his own position in that domain. Some sources say that through this marriage, Siward was then distantly related to Duncan; another version is that Siward's own sister became wife of king Duncan. This relation to the Scottish royal family would later affect the landscape of Scottish politics.
Siward was encouraged to settle disputes between his deputies Carl the Hold of York and Eadulf the Earl of Bamburgh, but was ultimately unsuccessful. The dispute had started in 1016 when Uchtred the Bold was murdered by Carl's father Thurbrand the Hold during the meeting with King Canute I. Eadulf had been Earl since the death of his brother Ealdred, Earl of Bernicia, Uchtred's oldest son, sometime after 1019. Ealdred had ended up killing Thurband the Hold to avenge his father and in turn Carl the Hold killed Ealdred.
In 1041 Eadulf III of Bernicia, the Earl of the North-East, was killed. The assailant was probably Siward, who became Earl of Northumbria. Siward continued to rule all of Northumbria from 1041 until his death in 1055. His marriage produced two sons, the older Osbearne, who died in battle in 1054, and the younger Waltheof, who eventually became Earl of Northumbria.
A kinswoman of Siward had married Duncan I of Scotland, and following Duncan's death at the hands of Macbeth in 1040, Duncan's infant son Malcolm Canmore fled south to the English court, coming under Siward's care.