Their baby was born dead (a still born). Rubi is the Demon King's 7th kid (bio related). Valid wishful thinking though
GIRLLLLL I CAME BACK FROM THE SPOILERS AND GUESS WHAT ..
(Spoiler so don’t proceed)
SHE IS THEIR DAUGHTER ヾ(☆▽☆)
Wha-... How??
in one of the most recent chapters, she has a headache from repressed memory and the demon king had a weird line about "the one he took" or something like that and she's the se age as the lost daughter. the mage probably faked her death by exchanging her with an actual stillborn
Oooohhhh, ok thank you
I JUST GOT NUKED FROM THE SPOILERS. HOT DAMN. WELP. YOU WERE SPOT ON G!!!
I said this based on what I read but I was wrong so ignore my comment
See. I guessed the story, right. I'm a huge fan of cute babies novel/story
I think they are her real family. Remember the reason why the Duke's family is angry at the mages, is when the Duchess involved in an accident with the scheming mage while she's pregnant. That's when I think Rubian is really their son (daughter).