Aragorn is the character J.R.R. Tolkien describes as the heir of Isildur in The Lord of the Rings.
Aragorn is introduced as Strider, a Ranger of the North who protects travelers in the wild. He belongs to the line of Isildur, the King of Gondor who cut the One Ring from Sauron’s hand but later lost it. Aragorn’s ancestry makes him the claimant to the crowns of Arnor and Gondor.
During the story, Aragorn becomes one of the nine members of the Fellowship of the Ring. He helps defend the Free Peoples, leads armies against Sauron, and accepts his royal identity. He is crowned King Elessar after the War of the Ring.
Boromir and Faramir are also connected to Gondor, but neither is Isildur’s heir. Éomer belongs to the royal house of Rohan. Aragorn’s lineage is therefore a specific genealogical fact, not simply a title given to any heroic leader.