Comment by yuriyuri on Akuyaku Reijou no Ani ni Tensei Shimashita - Chapter 7

Comment on ChapterAkuyaku Reijou no Ani ni Tensei Shimashita - Chapter 7
....ok, starting to see something. They mentioned before that in the story, Cain had nothing to do with his sister because he never got attention from his parents and was resentful. And they've shown this a few times with his parents kind of realizing their mistake. 

But the first time his dad takes interest is to push him to get closer to the prince against his will. Obviously it's not a terrible thing, but still shows that he doesn't really do nice things for Cain.