One of JRR Tolkien’s ideas for Aragorn’s backstory in The Lord of the Rings was that he was actually just three or four generations removed from Isildur himself.
Then how did he survive for the thousands of years between the Second and Third Ages?
The story goes something like this:
Many hundreds of years ago, young Aragorn fell in love with an Elven woman, who exactly resembled Lúthien Tinúviel in shape and outward form.
She called herself Arwen Undómiel, the Evenstar.
He fell for her, and romanced her, and gave himself to her; together they lived in her kingdom, where her magic and her power slowed Time to a crawl for them, while hundreds and hundreds of years passed in the world outside.
At first, the Elven-maid seemed every inch a queen: beautiful, graceful, soft-spoken, meek, and with the manners befitting an upbringing in Valimar long ago.
But over time, Aragorn came to realize that his beloved had a hard, greedy, grasping side, even a cruel streak, which more and more showed itself in unexpected flashes.
Worse, she was not who she seemed to be.
Eventually Aragorn pieced together the secret.
His bride was Sauron, divested of her usual male disguise.
Greatly weakened by the loss of the Ring, Sauron yet maintained strength enough to craft a prison for the heir of Isildur: a false realm of hollow bliss and sterile delights, where the one she thought was the greatest threat to her power could languish in eternity.
A part of herself, wearing a female aspect – the gender she had hidden long ago in the deeps of time, to gain entrance as an apprentice to the smithies of Aule – remained in this pocket world, as Aragorn’s bride: a plaything to keep his attention from the bars of his gilded cage.
But eventually, Aragorn figured it out.
Eventually, Aragorn escaped.
Thousands of years had gone by in the world outside since Aragorn had been ensnared by Sauron.
Now, emerging from long captivity in a magical sub-realm, he studied the world around him, and learned what had changed and what had endured.
He met Gandalf, and learned much from the Grey Pilgrim, and taught him some things of his own; and, in search of information, he pursued and captured Gollum, who had possessed, and been possessed by, the One Ring for so many centuries.
And, shortly before his ascent to the throne of the reunited Kingdom of Gondor and Arnor, he met his future bride: Eowyn Elfsheen, sister-daughter of Théoden, King of Rohan.
(PS: Christopher Tolkien or another amanuensis may have written this story down as part of the Secret Library Archive Project.)