It is mentioned in the Hobbit that Bifur, Bofur and Bombur are not descendents of Durin but are of the people of Moria dwarves.
This confuses me, since Durins folk is strongly tied to Moria:
- Balin tried to reclaim it sometime between the events of the Hobbit and the Fellowship.
- Thror too tried to reclaim it from the orcs after his people had to flee from Smaug and give up Erebor.
- Durin VI was King of the Dwarves of Moria when the Balrog was woken and killed him.
To summarize, I always assumed that Moria was a kingdom of Durins folk (like Erebor, the Iron Hills and the Blue Mountains) but it is explicitly stated that Bifor, Bofur and Bombur are not descendents of Durin.
This begs the question: Who exactly are the Moria dwarves? Which I asked here: Who were the seven forefathers of the Dwarves?.