Dear Grandparenting: It embarrasses me to relate what my daughter did. She had an affair with a neighbor three houses down the street. Nobody was the wiser until she got careless and left her computer open when she went to the bathroom. My son-and-law comes by and sees her little love note. End of marriage.

I was floored. That was five weeks ago. When I asked her why, she said she fell hard for the guy and “love is a battlefield.”

My two young grandchildren are smack dab in the middle of all this. My daughter thinks kids can adapt to anything. Why do people think they can get away with this stuff, like there’s no harm done? My grandson is eight and my granddaughter nine. Anonymous, New Canaan, Connecticut

Dear Anonymous: We don’t pretend to understand the mysteries of marriages, why some work while others fail. In our experience, it’s often harder to figure out why certain unions endure.

Infidelity is frequently a manifestation of other marital issues, as partners emotionally check of their relationship before the cheating starts. Technology plays a dual role — an easy means to shop around for a fling, and a means of preserving incriminating evidence.

Numerous online studies track the impact of divorce on children. Mental health professionals frame the problem in terms of “attachment theory” — the glue that that bonds parent and child and comes in to play during subsequent romantic relationships. Divorce, goes the thinking, imprints children with a poor model of commitment, since they anticipate betrayal and abandonment.

Prevailing wisdom indicates that your grandson is more likely to “act out” in school and social settings, while your granddaughter’s reaction is apt to be delayed. Younger children are more vulnerable in the near term, but many eventually adjust better than do older children.

Grand remark of the week

Sam Hall, from Waynesboro, reports that he gives each of his grandchildren equal treatment. “I remember their accomplishments and forget their mistakes.”