How do your sims react to being unfaithful?

I wish I knew how to post pictures here, one day I decided to change my stories up a notch and make one of my Sims cheat on his lover(former-lover now) and I felt so bad for doing it :( he got so angry and my Sim got so Sad - it might be deserving he feels that way but I actually made a Sim try to flirt with him and I almost gave up because he kept rejecting any flirtatious interactions from anyone but his lover at the time, then he cracked, it was soo sad, his best friend tried to cheer him up but she only made everyone angry... darn.... good thing I have two saves... what's worse is that the one who was 'seducing' him was his lover's sibling.