I don’t think that’s the case, honestly. I really think it’s because the current duke and all the previous ones are insanely obsessive and possessive as the story dictates. Perhaps the duchess was taken by force very early on before marriage and conceived Albert through the r*pe, rather than any case of infidelity because their super rare silver hair is an exact match and Albert does take after his mother, according to the first chapter that Viola met the duchess, Helena. His mother, as cruel and mentally/emotionally twisted as she is, does not want her own son to be like his father.
There are a few cases where the genetics of serial r*pists/killers have been passed down to their children or grandchildren. Maybe that’s the take of this story, where the “sinful blood” is just a damning way of describing how the extreme greediness makes up the bloodline as a whole. Because if you think about it, being too greedy is considered a sinful thing. And some people in real life will get what they want, regardless of what method they have to use.
I hope what I said makes some sense.
But at the same time, all she is doing is making more victime.
She herself is obsessed in that case and even hurting / killing ppl, all to prevent him from doing the same...and at the same time cursing the blood in his vains.. when she is doing the same obsession but in reverse.. hurting ppl to keep him away from them.
That makes even less sense to me.
Here what I think from her comment about not being able to bloom like the roses because of love, the mother had high expectations of herself in high society but her single life in high society was cut short by the duke since he fall in love with her and done everything he can to make her his own and locked her up from the high society life she dreamt of which made her resentful towards her husband entire bloodline including her son whom was within reach for her to vent her hatred on
From my understanding after chapter 12.. it seems Ml may not be his mothers child as she stated he needed to learn the sins of the blood he carries (aka the fathers side).
The father may have been unfaithfull and Ml the result of that, hench why the mother "destroys" any and everything he loves to teach him not to love.
It does not seem to me that the mother loves Ml or has any romantic feelings for him. It comes of more like she is punishing him as she enjoying watching him suffer, and the father... well he may be jelous of all the "atention" his wife is giving Ml and feel he is a rival for his wifes love (especialy if Ml isnt blood related to his "mother"), hench the father moving them away from Ml and getting Ml married.
The mother then comes to tjeck if Ml is starting to feel affection to torture him again, hench the interaction with FL.
Also Fl is way to trusting.. Girl the Ml fears his mother for a reason.. yet you have no sense of danger at all... even the servants shows dread at the mothers arival... like read the room.