Im thinking maria stole the child.
Bet the wet nurse did it xD its usually them
Or someone switched their babies
A bit impossible as MC's birth mother gave birth at home
Exactly most likely she was married to the priest since no one was there but the prince, it was probably a secret, but was probably forced to marry mustache man. Who most likely didn't treat her well making her mental state deteriorate. Had the fl was accused of cheating mental state deteriorated more and the the mustache guy was like get rid of the kid.
Maria... Marianna... So that's why Millie doesn't resemble the mustache dude- she has a different dad because she cheated? But she doesn't really look like Maria either, except for the blonde hair... So that's unlikely. I can predict she was probably swapped at birth and hidden on purpose by enemies or was kidnapped then something went wrong (〜￣△￣)〜, based on what I glimpsed in the prince's flashback. Marianna probably died in childbirth. Now, if she's indeed the daughter (100% she is lol), how did she end up as Maria's daughter? Maria is pretty mentally unstable too... Lol what if her daughter died then saw baby millie then grab her thinking she's her daughter then with mental unstable, she forgot about it n idk