I don't think any woman in the world starts dating a married man on purpose.
Or at least that's what I would like to believe.
It just happens.
I am going to tell you why you should break up this type of relationship if you find your self at one at this precise moment in life.
I know it's hard. I also know it's also exhilarating, you think he is boosting your self esteem, he treats you like a princess, you never fight (except when you want more), sex is great, this is the best