Cindy is a Niflheim clone.
This would mean that Verstael is her father, and Cindy and Prompto are related (brother and sister).
Cid said Cindy saw her parents killed right before her eyes. It doesn’t mean they were her blood patents.
Take a look at their last names:
Argentum = Silver; Aurum = Gold
There’s also a theory that the Naga in the cave is Prompto’s mother. Poor Cindy…
What do you all think?