A thing about being older that is you pivot, at a point, from looking forward and into looking into a future that wasn’t but could have been. It’s not quite a tense in grammar, although it should be. The French futur antériuer is close. The future past.
So let’s talk about Elrond and Aragorn and what their relationship might have been like from the point of view of Elrond. The generations of Elves don’t follow what you’d expect, because they live forever, but essentially it’s this: Elrond’s daughter Arwen is Galadriel’s grand-daughter because Elrond’s wife (Arwen’s mother) was Celebrían who is herself the daughter of Galadriel.
Galadriel was perhaps the most powerful and longest-lived Elf in all of Middle-Earth. At the time of the telling of the Lord of the Rings she may have been some 15,000 to 20,000 years old. Quite literally years weren’t even invented before she was born, which makes it hard to tell exactly. She was also one generation away from Elf-kings who were powerful enough to fight gods in single combat.
Elrond, on the other hand, is directly descended from a god. His grandmother was Lúthien, the foundation of all of Arnor and Gondor through their grandson (and Elrond’s brother) Elros. Lúthien’s mother was Melian, a god, which makes Elrond 1/8 divine and Arwen 1/16, although with her heritage through Galadriel this should be modified upward because of previously-mentioned god-fighters in grandma’s line.
And all of that was coming to an end in the time of Aragorn and Arwen. There would be no more contests between mighty Elf-lords and Melkor. The last of what was left of that era, Smaug the Dragon, was by now put down. The “Necromancer” had been driven out. (The Balrog may have either been sensed by the White Council and discounted or unknown to them.) What’s this look like then, to Elrond?
“Remake the kingdoms,” he says, “to be worthy of my god-descended daughter.” This is Aragorn’s stated task. But I don’t think Elrond meant it quite like a condition. I think instead he was looking for something to hope for. You get to a place where from the outside you’re seen as a crab-ass meddler, trying to make your kids fit into what you hoped they would become. You don’t mean to be that person. There’s just so much you hoped this world would turn out as, for her, by her, and none of it ever did. There must have been a moment when Elrond looked on Arwen as a newborn and wished so much for her that never came to pass. He gave her everything that he could.
Here comes this 14th-estranged lesser cousin, Aragorn, thinking he’s the answer. Are you kidding me? Yet inside I think he was thinking, “Give me something to hope for before the end of me, and the end of of us all, and everything that happened.”