The Dunedain of the North and of the South

[Earniel]

After the fall of Fornost and the death of Arvedui, all heirs of the royal line were fostered in Rivendell. Without the protection and secrecy that Elrond's House offered, I doubt the line would have continued the way it did. Still, much was riding on Aragorn, if he came to perish, that very likely would have been the end of the direct line.

Gondorean Dúnedain were no less harried, perhaps even more so as the heirs of Anárion didn't have the option of raising children in hiding. The Kin-strife for example undoubtedly removed quite a few kin-lineages and heirs from the royal line by death or exile in Umbar. It also brought in new blood from the people of Rhovanion. A deadly plague further diminished the Southern Dúnedain. And then there were quite a bit of wars with Easterlings, Haradrim and Corsairs. I'm not surprised that after all that, they had a bit of bother finding a King with enough lineage to be called King.