Finn was one of the eight children, seven brothers and a sister, of Árni Arnmódsson or Armódsson, a lendmann, and his wife Þora Þorsteinsdóttir (daughter of
Thorstein Gallows). Finn was married to King Harald's niece Bergljót Halvdansdóttir, the daughter of Halfdan Sigurðsson (
Halfdan Hadafylke) and sister of
Sigurðr Sýr. The main source for Finn's life is
Snorri Sturluson's
Heimskringla. Finn and his brothers
Kálfr Árnason, Árni Árnason and all appear in the sagas. Snorri rendered an episode where Finn insists on King Olaf's behalf that
Thorir Hund provide remedy for the murder of Karli, one of the king's courtiers. Kálfr governed
Trøndelag under Olaf Haraldsson. In 1028, Finn and his brothers Árni and Þorbergr together with
Rögnvald Brusason accompanied Olaf Haraldsson into exile in
Kievan Rus. They returned with him, fighting at the
Battle of Stiklestad in 1030, where Olaf was killed. Kálfr Árnason was one of the leaders of the opposing army. Under King Harald, Finn held the manor and lands of
Austrått on the
Ørlandet peninsula in Trøndelag. In 1051, his brother Kálfr was killed in battle serving King Harald on the island of
Funen. Finn believed King Harald had sent Kálfr to his death on purpose and turned against the king. He left for Denmark to serve King Sweyn, who made him a
jarl and appointed him to rule
Halland. In 1062, Finn fought in the
Battle of Niså off the coast of Halland between King Sweyn and King Harald. King Harald was victorious; King Sweyn escaped, but Finn, who refused to flee, was captured. King Harald spared his life and set him free in Halland. ==Children==