Sims jealousy has been a little disappointing for me. Apparently a lot depends on what is done within the line of sight of the spurned spouse. My Sim had a lot of romantic interactions, including hugging and kissing, with his married girlfriend while on a date at a bar with her. Her husband was there, but his back was to them and he did not respond. Later the ex-husband used to come over to visit his little girl. I noticed that if my Sim would answer the door, his relationship bar with the ex-husband was in the red, but I never saw the ex be mean or try to fight or anything.