The House of Isildur were the descendants of Isildur, elder son of Elendil. The House came close to extinction at the beginning of the Third Age, when Isildur, his brother, and his three eldest sons were lost at the Disaster of the Gladden Fields. His youngest son, Valandil, was kept safe in Rivendell during the catastrophe, and so from him came the line of the Kings of Arnor that led over three thousand years to Aragorn II Elessar.