[William Cloud Hicklin]

Yes, I see what you're saying.

I think really we have another bit of Tolkien creating a bind for himself that he never cleared up, if he even noticed the problem at all. The Seven Rings appeared, almost ex nihilo, in the Ring-verse. The idea of the "Seven Houses of the Dwarves" came rather later but was, I'm pretty sure, derived from it; it made sense and still does that Sauron gave a ring to each Dwarf-king.

The problem came, as so many did, from trying to ret-con the new material into the existing legendarium, and the incompatibility of having seven dwarf-kingdoms in the Second Age but two major ones from the old legendarium which going by the LR weren't there any more. There isn't any real solution except by artificial rationalization, and unlike Tolkien we don't get to re-write anything.

And then there is something of a how-de-do with the idea that four, count 'em, four of the Dwarf-rings were lost to dragon fire. There are certain geographical problems posed by that.