I don't know what piece of lore you've gotten that idea from, so I can't support or deny it's truth based on any source. However, I will say that I believe that all life started on Tamriel, according to a statement made by Nu Hatta in the Nu Mantia intercept text.
Just to clarify, I was saying that regardless of any common ancestor, Nedes in particular were present before the Nords invaded, (or came back). Kurt Khulmann seems to imply that saying the Nedes descended from common Nordic stock gives weight to the Septim line's claim, and is therefore continued in the Empire, but proven incorrect. http://www.imperial-library.info/content/forum-archives-others
I guess what it really boils down to for me is:
Why is it that the Nords believe that Alduin will come and destroy the world and everything in it cyclically (always starting with the Nords), but nobody else seems to have a direct mirror to this story? (at least that I've seen. I would be happy to be pointed to them and beg everyone's pardon if I just missed it)
Others may have their end of the world story, but as far as i know, not one that has already happened before.