By the way there's a "tolkien-movie" website that says that Oín was killed by the Watcher in the Water. I never heard that before.

Well, I've just checked, and you're correct: ~The Bridge of Khazad-Dûm

It's not the answer I had in mind, but it's as good as. You may take the go now, in which case I shall reveal the solution I had thought of, or you may continue to guess at the original odd one out, as you please.

I admit to being stumped, but let's wait and see if someone else gets it.

None of these guys had children, did they?

Bombur was the only one that died at home