I am pretty sure the fact that Au Ra (Drahns) exist in the first is kind of indirect proof that they aren't related to Dragons.

Midgarsormr only came to the Source after the sundering, so there are no actual dragons in any of the reflections meaning they would've somehow would've needed to become related to Dragons without ever coming into contact with them...

It's mostly just that they LOOK Dragonic because of the scales, tails and horns, but there is no actual link.