I don't agree with the royal family part, specially since only a fraction of them deserves to be forgiven. I don't see any act of reflection from the King even after knowing what their ancestors did to the spirits so no
I get what you are saying, but in my mind I just think that the King is only like that because he really wanted to be close to the spirits but you know he couldn't, so he was very jealous of the Hero/MC's Dad, which twisted his personality and world view. Like I can see the prince ending up like the King after being rejected by spirits and the MC everytime. And I just want a happy ending for everyone. Like don't punish the son for the mistakes of the father. And I don't mean that the King should be forgiven completely, just give him deep regret, have him express his want for spirits and possible jealousy for the hero, joy for his children to be possibly forgiven, and you have it be that he isn't able to contract spirits at all while the spirits no longer completely avoid him but most importantly his family.
One the uncle doesn't deserve to have children. He can't raise them properly with love.
Two stop with the isolation hang more with family, confront "mean guy" yourself.
Three Stop being stupid. If you're going stay away from everyone then don't even make contact at all. I would have preferred a love story where they tried to break the curse and she and the prince get together.
Four you can kill people like you can make a bomb, so start threatening them people if you have to.
Five I want them to save the curse spirits from their suffering and help the royal family.