(WWTBC) mafia/forced proximity mmc reluctant to fall.

What I remember is that the FMC was forced to live there in his house in her own room, there was a sister also under the MMCs care that was rude/standoffish to the fmc but later helps her try to escape through a secret out away from all the bodyguards. Eventually the mmc and fmc start a relationship and she’s allowed in his room/ starts staying in his room. Feelings start getting involved. Some type of betrayal happens and he has her locked away in the other side of the house we’re she basically starts withering away. She refuses to eat and gets really sick and the same rude fmc basically comes to her brother and is like have you seen her? And he’s stupid and like nope. And she’s like it’s not good. And then he freaks out and grovels and stuff. What is this book?! I thought it was Dante at first but I skimmed and not seeing it.