Q: My child returned to my home after his weekend with his mother and while he was getting ready for bed, he mentioned that his mother didn’t come home last night. He’s only 14. What should I do? What’s good ex-etiquette?

A: One of the most common mistakes co-parents make is to believe their children when they tell them something the other parent said or did. I will never forget the time my client’s daughter, a 4-year-old, told her father that “Mom and Billy” were sleeping together. The father said nothing to the mother, just filed for custody believing that his co-parent was frivolously sleeping with her boyfriend when the kids were around. Since they had made an agreement that their dates would not spend the night when the kids were with them, dad filed for custody. No conversation, just filed papers.

It turned out that mom and Billy fell asleep in front of the TV while watching a football game.

The implication is that your son was left alone, but I highly suspect that is not the case. You probably don’t have all the information and your adult mind went into overdrive when your child said, “Mom didn’t come home.”

But consider the following…

Does mom live alone?

How close does she live to relatives or friends who may have watched your son when she was out?

Could mom have arranged a sleepover at a friend’s home?

The bigger question is why don’t you know the answer to any of these questions? That’s the red flag. It tells me that you and mom need to improve your ability to co-parent, pronto.

When co-parents need child care, consider reaching out to your co-parent for help. That’s called, ”first right of refusal” and it is a standard clause in a custody order.

That said, first thing you do when you hear something questionable from your child is talk to your co-parent — don’t accuse, just ask for clarification and then work together in the name of your child. That’s good ex-etiquette.

Dr. Jann Blackstone is the author of “Ex-etiquette for Parents: Good Behavior After Divorce or Separation,” and the founder of Bonus Families, bonusfamilies.com./Tribune News Service