Not all souls are amouratine. Infact, it is very rare to find one.
I suspect people with echo are reincarnated pieces of an amoiratine.

That means:
Us
Minfillia
Arenvald
Krile
Unukalahai

We know that none of the scions were regarded by Emet selch, just us.

He could care less about Alphy, Yshtoka, Urianger.
He says we stand above our fellows (the scions) but still fall short.

And the whole plan was to sacrifice the new mortal lives like Yshtola to power Zodiark.

So, it seems most people are new souls and the sundered are rare.