House Elendil

The House of Elendil was the royal line of the Dunedain established in Middle-earth which ruled over the Realms in Exile of Arnor and Gondor.
Elendil, son of Amandil, escaped the Downfall of Númenor with his two sons, Isildur and Anárion. They sought refuge in Middle-earth, where they founded two kingdoms: Arnor in the north, and Gondor in the south. Elendil ruled both of these as High King of the Dúnedain, and from his descendants came the line of Kings in both the North-kingdom and the South-kingdom.
Elendil himself was slain in the Siege of Barad-dûr, and his elder son Isildur inherited the High Kingship. Two years later, Isildur himself, together with his three elder heirs, was lost in the Disaster of the Gladden Fields. His only remaining heir, Valandil, was only a boy, effectively leaving Arnor without a King. Thus the House of Elendil split into two lines. In the south, Isildur's nephew Meneldil had been left to rule Gondor in his uncle's name. Meneldil now took up the full Kingship of Gondor, and Gondor was ruled by his descendants for more than two thousand years.
When Valandil came of age, he inherited Arnor, the northern realm of his father. Valandil and his descendants ruled the North-kingdom for thousands of years to come.