I have a few different families/sims I play, but I also have my "own household" which I jump into with my pretend wife and my sim self once in a while just to play the game to play (no story in mind).
Now one time I had both cheat and it made me feel bad/very uncomfortable oddly enough - so I haven't repeated those transgression for them and actually went back to a save game long before it happened (like it never did) And it hasn't since for them.
Guess it felt too close to home (like it really happened) since he was me and she was well...my waifu XD
Now in real life I've never cheated or been cheated on, but based on how the Sims made me feel seeing my sim self cheat and get cheated on - I can't even imagine what it would be like in real life. So no thanks! lol.
Outside of them, I have other sims cheat and do all nasty kind of things to one another, which really should call for police involvement but they don't make house visits anymore. None of which bugs me or makes me feel bad. I even had a sim kidnap another sims kid and raise them as their own and convince them the "neighbors" we long term enemies (not her parents lol).
Although I also play with plots in mind, I expect certain things to happen at certain time so I never feel bad because its just part of the planned story.