I honestly didn't symphatize with what the Lion children (frick the family name are hard lmao) are feeling. They did contribute to what happened, and harshly speaking, this is just bad karma that they reap after all the things they had done.
On the other hand tho, I do understand why they're like that. They lost their mother early, and no children would want to get their mother replaced so easily (at least in their eyes), with a girl who was not even an adult and is only 2 years older than the oldest child. Then the father who had brought that 'new mother' died too, without explaining anything or even spending his last days with his children. Heck, he didn't even have any last letter or last will for his children, since his official last will is only the one about inheritance (saying Shuli was the one to handle it until Jeremy is an adult)... So yeah the children's actions are really understandable...
Frankly speaking, Shuli's miserable life is all Johanness' (Jeremy's father) fault, and he's lucky it didn't look like that because he's already dead. It didn't matter how many times this manhwa tried to say "Johannes was a good man, a great man in contributing to the kingdom", it doesn't change the fact that he dragged an unrelated, innocent girl to his family and politics problems and sacrifice her so that his children can naively has their innocence as long as they can. I sure think that if it's not for Johanness' idiot 'solution' to his problems Shuli would never have any problems related to the Royal Family and the freaking Church.