The mistress or side piece, wasn't married with kids, your husband was. The blame is squarely on his shoulders. That side piece couldn't do anything that your ex-husband didn't allow her to do. Both your ex-husband and the mistress are morally bankrupt people, and I'm sick and tired of women either glossing over a man's culpability in adulterous affairs, or directing their anger or in this case, trying to understand what motivated a woman to cheat with their husband. Even if your ex-husband's mistress happened to read this piece, I'll bet all she'd do is laugh and say, tell this nonsense to your ex-husband, he's the one who was married with kids. Which would be true.

Your ex risked it all, willingly by the way, to commit adultery, and his mistress didn't care one bit that he was married and neither did he. Some people are irredeemable and they don't care who they hurt. They want what they want and decency and morality be damned. His mistress is probably screwing around with another married man, and your ex-husband will probably cheat on whomever he's with now, and only old age, illness or death will stop him.