The Kings of Úri's Folk

It is important to know, when dealing with dwarves, something of their genealogy. They are a strongly family-oriented people, and their lineage is as much a part of who they are as their personality or their experiences. Indeed, among their royalty, there is a belief that the first of their line will reincarnate seven times before the end of days, and kings that bear this strong resemblance are declared as such and treated exactly as their ancestor himself.

It is also important to know that many of the dwarves of the Ered Luin are not, strictly speaking, Durin's Folk. Durin was the first of the dwarves, and his line makes up the lords in Moria, Erebor, and Aglarond, but the kings of Nogrod are of the line of Úri. This is why, among other reasons, the dwarves of the blue mountains did not follow King Thorin to Erebor, for though they are kin, they have their own lords and their own holds to think of. 

The lords of Úri’s folk are bold, warlike, and strong-willed, though distrustful of outsiders; particularly the elves, what few remain. It is believed some treachery in ages long past is still sore in the minds of both people, though by whom this treachery was enacted is unknown. Though they are belligerent, their battles in the caverns deep beneath the mountains stopped their armies from marching against the great enemy in Mordor, though the Firebeards themselves claim to have fought at Carn Dûm and Mount Gundabad in wars that are little known and entirely overshadowed by the return of the King and the destruction of the One Ring.

- From The Chronicles of Annúminas by Morwen the Chronicler, 21st year of the Fourth Age.