Spoiler warning!!!
So ferio does have his own children with varia, 2 kids but neither of them inherit the boreoti characteristics (black hair and the fangs of the beast).. what duke aust is talking about is something totally different that'll happen when they got to the palace, I can tell u if u want!
Okay then another spoiler warning here!!!
Varia ends up being possessed by one of the gods in the northern mountains after she gets kidnapped by Leonia's good for nothing sperm donor and taken to the northern mountains through the palace's northern gate. But Leonia and her father are required to be at the assembly as the current duke and the duke's heir and without the DUKE being there, they won't be able to have a vote properly (as far as I remember). So Leonia steals the badge from phileo's coat, this badge signifies that the holder is the only ruler of the boreoti dukedom. This by technicality makes Leonia the duke, even against phileo's wishes. Leonia then "banishes" phileo to penance for easily losing the duke's title to his young daughter by sentencing him to the northern mountains effective immediately (where varia is). It was the only way she could think of to get him there asap and save Varia. So she did "steal her father's title", this fulfilling he prophecy.
actually!!!
phileo and varia's first born (lea) inherited the fangs of the beast as well. that's why when lea was born, there were discussions whether or not making lea the next duke instead since she is technically the 'legitimate' child.
yknow how leo would joke before that phileo should marry and have another child and make them heir instead? well, by the time lea was born, leo already made up her mind to be the heir. especially when she already put on the effort on her lessons/studies. and lea ended up loving leo so much that she doesn't even want to be heir haha
btw for the beast fangs, it is always inherited by the first borns of anyone with voreotti blood. that's why lea also inherited it since she is phileo's firstborn.
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DID SHE?? I assumed not since i read part of the second book and it said that both of their kids inherited varia's looks, with one being a really powerful mage (lenius) so i assumed both didnt inherit but that makes sense! The translation i read was pretty bad :(( thanks for clarifying it for me!! Please tell me thought lea DID end up becoming lupe's wife and viscountess vikross didnt she? Or am i going crazy here?
Omg OMGG
Uhh, Lupe is the nickname for the current viscount vikross' son right? So the age difference is only like a year, maybe 2 years at most since varia will soon become the official duchess, give it a couple chapters and then gets pregnant within a week, although the pregnancy is very much off screen. Varia's first child bea becomes his fiance early on and they grow up tgather so no age difference. Sorry if I made a mistake I seriously thought the current viscount vikross' son's nickname was Lupe mb g
Maybe it's the same nickname or smth... I really have no clue what the son's nickname is. But duke phileo's assistant, aka the viscount vikross' currently had his first child recently in the mange right? That child is the one who gets engaged and married to bea, Leonia's little sister and miss varia's first biological child.

I kinda dont get the last part... isnt she the heir anyway? Or like will there be a son or daughter next that would possibly be and then she has to take it away..