If you ever watch TV shows like "Cheaters" and "The Maury Povich Show" you're likely to determine that neither sex is has a monopoly on cheating. I think both sexes cheat for the same reasons. My guess is it's probably still men who have the edge.
However if you include (secondary cheaters) those who knowingly pursue others in relationships or knew from the onset the person they were seeing was attached....etc
You can't exactly call those people innocent bystanders.
Some states are now allowing spouses to sue "the other woman" or "other man" for wrecking the marriage.
One such wife was awarded $9 Million!