Comment: So much judgement from commenters and the author.  Ya, the fact that the relationship started via mutual infidelity could mean "once cheaters, always cheaters", and that they must have a "cheating gene" deeply imbedded in their DNA.  But could it not also mean, that they might have been in problematic, unfulfilling relationships before? Abusive even perhaps? And when they met one another, they sensed an opportunity for a better life - together?, .. or actual love?  Oh I can already hear the moralistic responses - "If that were the case, they should have done the proper thing and ended their relationships before getting involved.....blah, blah, blah".  Sure that would have been "better" in terms of meting out self-congratulatory relativistic moral judgement - all I can say is it must be nice to always live in a world, where the choices are always so black and white, and others deserve every misery they get when they act without such absolute virtue.  Meanwhile, back in the real world...