I slept with someone who I knew had a boyfriend.

Was backpacking in 2018 - a woman in my group had been travelling for 3 months already, called her boyfriend most days. The group went on a party boat together and stayed in a hostel on an island, we were drinking and I asked her how she was doing keeping the relationship going long distance. She admitted she was getting bored/annoyed with him asking for sexting/nudes all of the time and that it didn't really do anything for her. A few days later we were staying in a city and went out with the group drinking and dancing, we stayed after everyone else left and she kissed me. One thing led to another and she was back in my room that night. We kept sleeping together (I like to think we were subtle but you rarely escape people's notice) for another few weeks until we went our separate ways. She's married her BF now and they have a baby on the way.