Review Detail of Cerisehun in The Wronged Heiress Reborn For Her Crown

I have a question. I haven’t read the book yet but I need to know. If her biological parents and her brothers are such bigshots then how did her foster family managed to kill both her parents and get away with it? They killed their parents but her biological brothers didn’t do anything and waited for her to get out of prison to expose her foster family? Bs