Hmmm... I'm thinking you have your stories crossed.
The story the MC is on right now used to be a novel her sister wrote back in Korea. In the original story, Kai was an actual tyrant that commited crimes. The bitch princess and Ares are the original lead characters, and Alicia is just a mob character that got caught in the action when Kai's supporters and family started to be cornered and beheaded by the revolution OG Ares and OG Princess started. Plus our MC actually suggested all of this herself when she was the editor of her sister's novel. It's one of the things I like the most about this story and why it's so memable. She brought the whole thing upon herself when she told her Korean sister to change the story to make it "more interesting"
I read in an spoiler that this story actually took place before and she is reborn as the character. The real reason why Ares killed the little brother and Alicia because he was fed rumors. As u can see due to scheming of uncle ,Kai couldn't get an appropriate education and he was used by the uncle and princess as they wanted to usurp the throne
She wasn't reborn or anything. Otherwise this would meant the current timeline will be her second life. The revised novel that the pre-transmigrated MC's sister changed the storyline where the brother(Kai) became a tyrant, hence being killed by Ares in that revised novel. I read the spoiler too, and MC was transmigrated, not reincarnated.
I still can't get over the fact that ML killed her and little brother in the previous life when that bitch fed him rumors and he believed in each of them because he was soo in love with her. He killed them for no apparent reason and without actually verifying the information. It gets me soo mad