NTA. I'm continually boggled by how many of these stories are posted about kids being full of rage at their stepmoms, and spending their lifetimes expressing their hatred in so many ways, while completely failing to see where the problem started: the dad's dick. Their lives have been upended because their father decided to pursue a hotter hole, never mind the fallout. Yes, there are plenty of cases where the first wife really was insufferable and divorce was best, but in those houses, the kids were just as ready for change. If dad needed another woman to persuade him to leave, he didn't have much character. They never seem to see that. Ironically, this is addressed in The Lodge. The dad, who is really responsible for the mess, is the one who finally pays.