books where one character is forced to be with another (who is eventually endgame) while actively in love with someone else?

this is a little specific but I’m looking for something where Character A is loudly in love with B, they were going to be together, no doubt about it. Maybe everyone knew that too. But circumstances force A to marry/be with C. C comes into the relationship hopefully, maybe looking forward to falling in love with A. They do too. But there is a lot of angst because of A’s derisiveness towards this sham of a marriage, their heart only belonging to B. He’s never going to love C (and for a good half of it he is devotedly in love with B). I would like A to be hostile to C (for trying to take B’s place but any reason would do). A ofc slowly falls in love with C but it nearly is too late. I’d like C to be kind of a gentle lovable character and for it to be heavy angst too if that’s there. If there is any book with this premise pls lmk i would be eternally grateful.