So, going off what I've pieced together and my own assumptions, Cecile is the daughter of ...

So, going off what I've pieced together and my own assumptions, Cecile is the daughter of the Grand Sorcerer. Add in this library of alternate worlds, I'm guessing the Grand Sorcerer was so grief stricken by her daughter's original death that she created all these alternate worlds in the hope that her daughter would live in at least one of them.

It's been a while since she was mentioned/I can't remember exactly, but didn't they say the Grand Sorcerer disappeared? It's probably because the amount of magic she used to create all the other worlds was so great.