On Game of Thrones, Bronn and Cersei never shared a scene together because Jerome Flynn and Lena Headey had a really bad breakup. I don't they were even on the same set together.Him and Adrianne Palicki got divorced, and so a lot of people think that means they won't be able to work together and one of them is going to leave the show.
Kind of makes me think of House a little bit, where two of the actors, Jesse Spencer and Jennifer Morrison, got together while their characters were together on the show, but they ended up breaking up in real life, while their characters were still a couple. I can'timagine how awkward that must have been.