Q: My ex is a liar and a cheater and about a year after I finally left him he decided he has seen the error of his ways and wants me to come back. He has been seeing a woman for about six months who has no idea that every time we talk (we have two kids) he tells me how sorry he is and would never do it again. Truth is, I was his second wife and he cheated on his first wife and me and both relationships ended as a result. Here’s my question. Is it good ex etiquette to warn this woman he’s been seeing that he’s after me and that he’ll cheat on her, too?

A: I am often asked this question — and my answer is no. Reason being, it’s really not your job to clear the way for this new woman. It’s your ex’s — in the sense that this is their time together and as ridiculous as this sounds — he may not cheat on her. Granted, a leopard rarely changes his spots – but after failing twice miserably, he may realize he just can’t do that if he wants a relationship to last. Then the question becomes, does he want this one to last — and if he doesn’t, it certainly isn’t your responsibility to be your ex’s relationship sheriff.

You have to ask yourself why you are even entertaining a heart-to-heart with the new girlfriend. The implication is that you would be doing it to save her the pain of falling for a cheater, but is that really it? Could there be a hint of revenge in your motivation?

If you tell her, one of two things might happen. First, she could think you are just jealous, lying, and dig her heels in deeper. This would start a cute little vendetta between you and her, not to mention alienate your ex — and you did say you have two kids, which means you need to build the co-parenting relationship, not drive a wedge in further. Second, she could believe you and leave, which would once again anger your ex — and make co-parenting difficult.

So, from an ex-etiquette standpoint, following the rules of good ex-etiquette, particularly rule No. 5, “Don’t be spiteful” and rule No. 6, “Don’t hold grudges,” and rule No. 9, “Respect each other’s turf,” the best thing you can do is begin to see him as your children’s father, not necessarily your ex who did you wrong, and move on. You opened your question to me with, “My ex is a liar and a cheater.” You already know what you are up against — best to keep him at a comfortable distance — always in the best interest of the children.

Dr. Jann Blackstone is the author of “Ex-etiquette for Parents: Good Behavior After Divorce or Separation,” and the founder of Bonus Families, www.bonusfamilies.com. Reach her at:

[email protected]