The Two Kingdoms founded by Elendil and his sons were originally intended to form two parts of a greater nation of the Dúnedain, ruled by a High King at Annúminas. This was not to be. The loss of Elendil's son Isildur in the Disaster of the Gladden Fields led to a chain of events that separated Arnor in the north from Gondor in the south, and the two kingdoms continued to follow different paths through history.

Arnor, the North-kingdom of the Dúnedain, was ruled by the direct descendants of Isildur, beginning with Valandil, his youngest son. Though the bloodline of the Northern Dúnedain came directly from the old High King, theirs was a troubled realm. Internal strife and war with Angmar saw Arnor become fractured and eventually destroyed, leaving the Dúnedain of the North a dwindled and wandering people.

Nonetheless, the line of Isildur was maintained through the Chieftains of this people. Aragorn II was Isildur's Heir through thirty-nine generations, and it was he who reunited the Kingdoms of the Dúnedain after three thousand years of separation.