By Melissa Chapman, New York City mom and author of WCBSTV.com's parenting blog.

When I met my husband over 10 years ago, I had the greatest of expectations. Like all gullible brides, I was blinded by the glittering diamond on my finger and brainwashed by fairy tales of white weddings and blissfully happy endings. Sure, my husband was 15 years older than me; my mother angrily accused him of being a Svengali; and he was living in an apartment that had carpet on the walls (more on his apartment in another post). To my mind, these were all minor hiccups on my road to wedded euphoria.

But nothing could've prepared me for the insanity of my in-laws.

When I initially met them, they struck me like any other couple who's been married for 30-plus years: They seemed to tolerate each other. But there was much more to the story. My future mother-in-law was suffering from multiple sclerosis, and this gave my future father-in-law a convenient excuse to indulge his roving eye. While she sat home every night, and MS began to ravage not only her physical health but her mental faculties as well, he'd found a married woman whom he had begun to--not so secretly--date.

By the time I joined the family, he'd been carrying on this affair for several years, and although I thought his behavior was beyond deplorable, my husband and two brothers seemed to sanction it under the guise of "Well, our mother is sick, so why should he have to suffer, too?" Believe me, I've engaged in many screaming matches with my husband about his apathy about the whole thing.

When my mother-in-law passed away eight years ago, this married woman came to pay her respects. While I was ready to give her a good backhand across her face, my husband and his brothers politely pulled their father aside and told him to ask her to leave.

Let me paint a more vivid picture for you: This woman lives with her retired husband. They're both in their 60s. My father-in-law, at the ripe old age of 77, hangs out with the two of them every day! According to him, her husband has no idea that they're doing the nasty--several times a week, as he likes to boast. Her grandchildren decorate copious love notes for my father-in-law, which he proudly displays on his fridge (I'm still not sure where my kids' drawings are stashed!)

The truth is, if I lived a few hundred miles away and just saw him on holidays, I could file my father-in-law away in my brain as nothing more than an old coot. Unfortunately, we happen to live five minutes from him by car. And his married girlfriend and her husband? They happen to live right around the corner from my parents, the only grandparents who actually spend time with my kids. So every time we do a drive-by, my daughter immediately asks, "Why is grandpa's car at this women's house? Why does he hang around with her and her grandchildren? Why doesn't he ever come and visit us?" I tell her I don't really have any answers, although I'd like nothing more than to malign this man.

Do you think I'm coming down too hard on my father-in-law? That I should just leave him alone and make peace with the fact that he is just not interested in his grandkids and that he sees nothing wrong with dating a married woman and exposing their relationship to prying gossip mongers? And what can I possibly tell my daughter?