Q: I am quite good friends with my husband's ex. At first, it was awkward as the kids went between homes, but as time has gone on, I find we have a lot in common. Recently she has started confiding in me — she's having an affair with a mutual friend's husband. I am so conflicted. Where should my allegiance lie? If I tell our friend, it could get back to her that I was the one who passed on the info and screw things up with my husband's parenting plan. If I stay quiet, I feel like I'm condoning her behavior. What's good ex-etiquette?

A: Oh my. You've got yourself in quite a predicament — and it's the chance you take when you're friends with your husband's ex. It's a very tricky relationship. You will always be weighing allegiances, so it's best to establish personal boundaries right now.

Hands down, unless your husband has betrayed you in some way and you are in the midst of moving on, your primary allegiance is always to him. Therefore, if something you might do will affect his life in a negative way, you don't do it. We all have friends, and sometimes we confide in our friends about our partners — her breath stinks, he wants or doesn't want sex, she leaves her underwear on the floor, it drives you crazy when he doesn't put the toilet seat down — these things are standard gripes between friends. But, they won't affect your partner's life.

Outing his ex might. That's why this sort of relationship is so tenuous and why I always suggest, "cordial, not cuddly" when dealing with an ex — his or yours. You cooperate for the sake of the kids. That's your mutual interest. That's your boundary. Period.

So, using that as the criteria for good ex-etiquette decisions, strip away all the adult drama and ask yourself, is her behavior affecting her ability to properly parent the children? If it's not, there's your answer. Stay out of it. If it is, then you have an issue to consider and you have to figure out exactly how passing on the information can serve the children.

Just remember, if you want to say something because her behavior goes against your personal morals and you think custody should be changed as a result, the courts and/or Child Protective Services will not step in if a parent is having an affair or moving someone in too soon. It's when the kids are no longer safe that the courts or CPS steps in. If the kids are fed, clean, going to school on time, etc., the courts and CPS will not get involved.

At this point, I suggest you wait and watch. As much as I hate to suggest it, people's motivation can be shady at times, and she may be testing you simply to see where your allegiance lies. That's why it's so important to make sure everyone — not just the ex — knows your allegiance is at home. That's good ex-etiquette.

Dr. Jann Blackstone is founder of bonusfamilies.com.