With Sumarlidi and Einar in winter Joint earldoms were a frequent feature of the Norse earldom of Orkney and usually one of the partners was recognised as the senior figure, responsible for military activities. However, such arrangements were often unstable and the
Orkneyinga saga is less than explicit about how these shares were divided up geographically. It is possible that Brusi's share, described as the "northernmost part of the isles", was those islands lying north of the
Orkney mainland, that Einar's was originally the east Mainland and the south isles and that Sumarlidi's was the west Mainland. However, it is also possible that Brusi's share was
Shetland, which formed part of the earldom throughout the Norse period. This possibility is supported by a later reference to his son
Rögnvald as "Lord of the Shetlanders" and Thompson (2008) is in "no doubt " that Shetland was in Brusi's possession. The Shetland island of
Bressay may have been recorded in 1263 as
Breiðoy (
Old Norse "broad island"). However, in a 1490 document the island is referred to as
Brwsøy - "Brusi's island" which name may indicate it was Earl Brusi's 11th century base. Sumarlidi died in his bed not long after his father. Einar took his share, ruling two-thirds of the Earldom with the remaining third held by Brusi. Einar soon became unpopular, demanding heavy taxes and frequent military service from the farmers, and gaining little booty on his raids. He was, the saga says, "a great bully", whereas Brusi was "well liked by everyone".
With Einar and Thorfinn , the site of Thorkel Fosterer's hall, Hlaupandanes, on the east coast of mainland
Orkney. and Brusi had to make peace between the two when Thorfinn grew to manhood, not once but twice. On coming of age Thorfinn asked for Sumarlidi's third from Einar but the latter refused. Both raised an army so Brusi also raised a force to come between them. He forged a peace treaty in which it was agreed that Thorfinn should get his third and that on the death of either of the other two brothers, the surviving one would inherit their share.
With Thorfinn When Brusi inherited Einar's third of the earldom Thorfinn was not pleased with this arrangement, and asked Brusi for a half share. To find support Brusi went to Norway, to the court of King Olaf, to have the sharing out of the Earldom settled and Thorfinn followed him there. Olaf forced both of them to accept his overlordship and kept Einar's share for himself, (as reparation for Einar's murder of Eyvind Aurochs-horn) appointing Brusi to administer it, and kept Brusi's two-year-old son
Rögnvald at his court. Brusi later gave control of Einar's third of the islands to Thorfinn in return for his seeing to the defence of Orkney and Shetland. The
Heimskringla then tells that at this time, when King Olaf was defeated by
Cnut the Great and exiled to Russia, that he was joined there by Rögnvald Brusason. Rögnvald later fought in the
Battle of Stiklestad in 1030 where Olaf was killed. and the
Orkneyinga saga that he had died before his son Rögnvald accompanied
Magnus the Good back to Norway. ==Succession==