Dude needs to clear up the misunderstanding(s) cuz rn he's in the dog house.
From what I gathered with 12 chapters; husband arrived to the scene of her murdered parents and mansion on fire, ex-fiance is most likely the evil prince who's fighting for the throne against his sister, and there's some k8nd of time travel or regression where the husband lost the MC.
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.
They're so precious