Q.My 8-year-old grandson -- a problem eater for years -- likes fast food best and won't eat anything at all at a party, even though he likes what he is offered and is hungry when he gets there.

I think anxiety affects his appetite at parties, but my son -- his father -- is a police officer and he sees each disagreement as a power struggle between them.

He and the boy's mother, who is also a police officer, are divorced, married to other people and now in their thirties. They have agreed to have their son move back and forth, from one house to the other, so they can each spend time with him.

Both his father and his stepmother are stressed, sleep-deprived and very frustrated with the boy -- a healthy, athletic child who stutters and is medicated for attention-deficit disorder. He is also sure that his stepmom doesn't like him, but he doesn't seem jealous of his three half brothers, who are between 3 months and 2 years old.

The eating problem erupted recently at a family birthday party when my son tried to force the 8-year-old to eat his noodles. I know grandparents shouldn't interfere unless they see abuse, but I just couldn't watch a child's happiness dissolve into tears, so I quietly pleaded with my son to wrap the food and handle the problem at home. Instead he grounded the boy for a week and wouldn't let him go to a professional basketball game, to which he was looking forward.

Ever since the party, my son and daughter-in-law have been furious with me and won't let me see the children at all, even though I was their primary babysitter.

We used to get along so well. How should we have handled this problem? And how should we handle it now? I really miss these children.

A.You should handle this problem, and any other disagreement in the family, by apologizing, whether you think you were at fault or not. Family squabbles only endure when each party tries to blame the other.

Although your wish to protect your grandson is understandable, you don't have the right to tell anyone how to rear his child, even your own son.

There may not have been a scene if you had asked, "Do you want me to try to get him to eat?" or "Can I be of help?" Your grandson probably wouldn't have cooperated with you, either, but you might have kept your son from blowing up.

Once they accept your apology, stick to your role as sitter and grandmother.

Your job is to rock babies, read to small children, tell family stories and make cookies. This work will be deeply appreciated, because no one else has the time to do it.

Look also for a parenting class that you -- and perhaps your son and his wife -- could attend, since it sounds as if all of you need new ways to handle an 8-year-old with ADD.

The Faber-Mazlish workshops are particularly good and so is the advice Adele Faber and Elaine Mazlish give in their classic book, "How to Talk So Kids Will Listen & Listen So Kids Will Talk" (Harper's, $13.95), based on the kind and gentle teaching of Haim Ginott.

The parents, stepparents and grandmother all need to change the eating habits at home, too, so your grandson will learn to eat healthy foods. You do a child no favor by giving him fast foods, because they contain too much sugar, salt and fat, which only makes a child want more of the same.

Instead, tell him that he'll do better in sports when he starts eating fresh fruits and salads, multigrain breads, organic foods and natural peanut butter. He'll still want fast foods, but keep saying no until he learns to like healthy foods better than anything else.

He may not go along with such radical changes at first, but that's all right. Just tell him you know he'll eat when he's hungry, if not today, than tomorrow or even the next day. If you push him to eat, food will definitely turn into a power struggle with you, his dad and everyone else.

You shouldn't urge this anxious boy to eat at a party, either. Instead, have him eat at home before he goes and just nibble a bit when he gets there.

Questions? Send them to advice@margueritekelly.com or to Box 15310, Washington, D.C. 20003.