Sims still flirt after breaking up..?

Yeah..... sometimes that old chemistry is still there below the surface ;)

Of course. Romance, as most interaction groups is broken, it always has been. Dont get me started with unknown mind states that suddenly happen that will lead to break a relationship or to just start losing empaty at half bar per second until its almost empty again.

Sims in the Sims 4 have always been far to flirty and there doesn't seem to be any rules in place to stop them. Broken up, married, they don't care. They will flirt with other sims no matter what. I play rotational and almost every time I switch to a different family they will have extra romantic relationships that I had nothing to do with making. I almost always have to use the MC Command Center to remove all the extra relationships. It's something that really needs looking at and fixing by the developers but like with most things in TS4 it probably won't happen.