from the looks of it I think they also spoiled arke, and too much at that, as they say too much over protection to your children will cause more harm then not, its like not letting your children have the proper vaccines
I don't get that hate you have.
Arke was adored by her family. They loved her dearly and tried, in their own misguided ways, to help her. They're stuck in a political situation where they have to maintain neutrality, that's their whole schtick. They tried to tell the newspapers (which are only a decade old in this story so defamation prob doesn't have regulations yet) to stop but the empress and her cronies backed the newspapers. The chiefs claimed the Brights were pressuring them and the public ate it up. Public opinion also tied their hands.
Arke also did not tell them she was struggling and being cheated on. She didn't want to hurt them and they didn't want her to get hurt so they ended up hurting each other. Yeah, the dad being distant but doting and the grandfather getting strict wasn't the ideal way to cope, but they're also being hurt by this. Arke also wasn't a perfect angel.
They knew about Iris, but divorce and all that jazz so having her here now means they can finally dote on her, too. They love Arke and Iris but they feel guilty about Arke. They've learned the truth and are taking steps to not repeat the same mistakes.
I hate the dad and the grandfather cus of how they treated arke and now they're spoiling iris, I don't get it because the story just seems like iris is just getting pampered since she's a child getting loved by everyone while arke is so pitiful and she should've gotten the love more