"Until the 880s there were no kings in Norway, though ancient sagas gave this title to a jarl - a Scandinavian earl - who ruled over one of the numerous small territories of Norway. Their principal occupation was to fight other jarls, in the hope of acquiring their land. Land ownership was vitally important. Land was the major provider of wealth, and wealth was the sole means of securing the loyalty of those who fought for you. The present-day Mafia boss would understand the importance of this. The warring jarls also understood that when their quarrels reached stalemate, another tactic, in securing and adding to their land, was to marry a son or daughter advantageously. As you continue to read, you will see the repeated interlinking of a relatively small number of families, so as to protect and acquire land.
The following account of the Jarls of Norway derives from Norse sagas. One point of view is that the sagas are not accurate accounts of history, and contain their fair share of exaggeration. An alternative view is that the sagas accurately portray historical events, being passed from generation to generation in verse before being later committed to parchment without any alteration. [Knut Liestol, Origin of the Icelandic Family Sagas, 1930.] I would expect the truth to lay between thes two extremes, perhaps on the side of their accuracy, for one of the most remarkable features of these sagas is that they offer a consistent account of the families and events associated with them. They can be best viewed as historical novels - embellished, especially when speeches are assigned to leading characters, but not without historical substance.
The preface to the Heimskringla of Snorri Sturlason gives the case for sagas as accurate portrayals of historical events: 'In this book I have had old stories written down, as I have heard them told by intelligent people, concerning chiefs who have have held dominion in the northern countries, and who spoke the Danish tongue; and also concerning some of their family branches, according to what has been told me. Some of this is found in ancient family registers, in which the pedigrees of kings and other personages of high birth are reckoned up, and part is written down after old songs and ballads which our forefathers had for their amusement. Now, although we cannot just say what truth there may be in these, yet we have the certainty that old and wise men held them to be true [Snorri Sturluson, Heimskringla, or The Chronicle of the Kings of Norway, c. 1225, English translation by Samuel Laing, 1844. See also F. W. Horn, History of the literature of the Scandinavian North, from the most ancient of times to the present, 1884].
So look up the books and read the stories. It may be the only information to gather during these eras.n.b. Heimskringla is comprised of a number of sagas, such as Ynglinga Saga, Halfdan The Black Saga, and Harald Harfager's Saga. They will be quoted henceforth, as translated in Laing's work."
Source: THE ORIGINS OF THE STANHOPE FAMILY