Not me, but actually my mom.

My parents had been married a couple of years when he cheated on her. They were going to divorce, literally days away from filing the paperwork, when she found out she was pregnant with me so they stayed together.

Fast forward 15 years. My parents have a great relationship as far as I am aware. Then my dad goes into midlife crisis mode and cheats on her again, this time lasting a few months, with her best friend, his secretary, and his cousin. He eventually admits it, but my mom has a mental breakdown and is essentially bedridden with depression for several months. Since she can't really talk to anyone else, she vents to me. Part of it is to help her cope, but part of it is to make me hate him so she gets custody in the eventual divorce. One of the things she did was explicitly tell me the stuff that he did. Awkward doesn't come close to describing it. You haven't lived until you've heard your mom say that she didn't blow him enough so your father fucked his cousin in the ass instead. I should add here that we're not white trash. If anything, we're aristocracy, which made it so much worse. They fought constantly for a year. He was legitimately trying to fix things but she was understandably psychotic. We had to take sharp things from her several times. She told me about her plan to travel back home and send him pictures of her fucking tons of guys. It was a bad year.

They stayed together temporarily because she knew she wouldn't be able to get custody in her current state, and he knew she might kill herself. They went to counseling. My mom had always been religious but my dad never really cared a ton, he just went along with her. They had a whole spiritual awakening thing and it legitimately seemed to fix their relationship. It's been 4-5 years since then and their marriage has never been stronger. The only annoying remnant of the whole thing is that my dad now goes along with her every single time we disagree. I think they're in a good place, but I always do worry that he'll become disillusioned with religion and will fall of the rails again. This time, my younger brother would have to deal with it (he was around 10-11 when it all happened and my dad and I did a good job of sheltering him from it) and he's more emotional than I am so I'm not sure he'd be able to handle it that well.