Naveah is a daughter from the main that the father was in love with but bcs she was born from a commoner the father got a lot of criticism and hate that ruined his life so he hated naveah for being born bcs he had to experience a lot of criticism and hate from other ppl and thats why his life went to ruined bcs of her being born. The marchioness did trick him into marrying him but it didnt stop him from loving the real daughter bcs ig he thinks his real daughter is better than a daugther of a maid but it doesnt mean he loves the marchioness or anything
(correct me if im wrong tho im not 100% sure abt everything i said, its all just from my understanding)
I do know that in the noble society, it takes a whole lot to disinherit a legitimate child in favor of illegitimate younger one. It would be a huge scandal in a noble society, possibly requiring king's permission. It doesnt matter if Noveah is married off, since her younger sister will be eventually married off too. It would be different story if one was male and another a female.
I don't recall him disinheriting her, besides marrying her off to Wistrash which was a total 'valid' move in noble society. And if he did disinherit her, it probably was before her sister even existed or he could've just made up some bullshit about Neveah being trash and booting her. He also has not explicitly announce her sister as sole heir or that he was choosing one over the other.

Confused now. I though Noveah was a maid's daughter, an illegitimate one, that was acknowledged by her father as legitimate and then married off. Thats why he barely supported him. And second child, was legitimate one and his heir. However, it says that Noveah is legitimate one and younger one is illegitimate. And their father hated Noveah because her mother, the Marchionne, tricked him into marrying her. However, regardless of hate, a noble usually can't disintegrate a legitimate child in favor of illegitimate one.