
Ml's sister could have been another manhwa's mc with her intelligence and beauty.
Ml's sister x mc's brother would a good combination

I'd read the heck out of that!
Oooh! And it would be awesome if she was isekaied the same time our mc was, so she lived there her whole life, but was also from our world... I'd personally also make it so that the grand Duchess hasn't read the book and thought she had just been isekaied into some random fantasy world, but she LOVED this era, so she got really into running a ducal estate.

It’s going to be ruined for ducking fandom.bro if you have a problem just don't read it.It’s story is about the mc. Not about those other character.

Stories are narratives. Whether you like said narrative or not does not depend on the MC. Characters contribute a lot to stories and their writing can significantly impact the reader's view on the narrative.
It's good to have opinions, but it's objectively bad. It's predictable, forced, and annoying. The relationships that are getting forced into the story is NOT neccessary
I really sympathy her brother. If only they had better upbringing environment, maybe they could have been less twisted and more normal.
That pope deserves to stone to death