Q. My brother and his wife are a very hip couple living out West with their 10-year-old son.

He is a rocket scientist and she is an architect, but she doesn't seem to know what she is doing as a parent and resents any interference. She just says that she is trying to rear her child the way the native peoples did.

She breast-fed her son until he was 7, gave him only macrobiotic food for years and always had him sleep in their bed. My brother finally told her that the boy couldn't sleep with them any longer, but she refused to let him go, so now she sleeps with their son in his room.

In addition, she has never repainted the inside of their 100-year-old house and the old paint, which has lead in it, has probably caused their son's severe attention-deficit hyperactivity disorder. He is just learning to read after years of remedial classes.

What can be done?

A. You can't do much except listen to your brother, with love and understanding for him and as much as you can muster for your sister-in-law. But don't blame her for everything. If one person in a relationship is passive, the other will become more aggressive. Marriage, like nature, abhors a vacuum.

This hip couple deeply needs marriage therapy or at least a good parenting class. Without it your brother probably won't become the strong father every child needs and she won't find out why she is so afraid to let her son go.

Part of her fear, and her excessive, obsessive behavior, may be caused by her own innate anxieties. But she may also feel quite unloved, or she may feel guilty for working outside the house. The more time some mothers spend away from their children, the more they want to sleep with them at night, especially if they have only one child.

That's not the usual cause of the family bed, however.

Most parents get there simply because mattresses are much bigger than they used to be and because disposable diapers don't leak the way cloth diapers did. And, of course, it's easier for an exhausted mother to nurse her baby if she doesn't have to climb out of bed to get him and for the father to let him fall asleep on his chest afterward, instead of putting him back in his crib. It's so cozy.

Other parents deliberately choose to have a family bed for a year or two or even three, to strengthen the family bonds, and then find themselves stuck with it for two or three more years.

And then there are those few mothers, like your sister-in-law, who believe that a family bed is right and natural since that's what native people did.

The family bed does have an idyllic, back-to-nature sound to it, but primitive people probably slept in one bed because their huts were too small for two. Even in the Dark Ages, a typical home had only one bed -- a gigantic piece of furniture, heaped with buggy straw pallets, according to William Manchester's amazing book "A World Lit Only by Fire" (Back Bay; $15.95).

This bed not only accommodated the children, the parents, the grandparents and other live-in relatives but also the stranger who knocked on the door and needed a place to sleep.

The family bed is much more comfortable and hygienic today and a good idea if a child is sick or if he likes to climb into bed with his parents for some early-morning cuddles, but the child who sleeps with his parents all night, every night, may not learn how to fall asleep on his own for years.

A child should learn this basic skill in the early months, just as he should feed himself at a year, dress himself at 21/2 and make his bed at 3, no matter how badly he does these jobs. The more independent the child, the more confident he will be, which is particularly important for your nephew.

Few children are more aware of their shortcomings than those who have ADHD.

You can't do much about his attention deficit or his hyperactivity, but you can tell your brother that lead isn't the only cause of ADHD.

The British government sponsored a study on the effects of sodium benzoate and four yellow dyes on nearly 2,000 young children with startling results. Parents reported marked hyperactivity, even in normal children, although the scientists used only enough dye to color a teaspoon of frosting. You can read about this complex double-blind study online in the June issue of the prestigious Archives of Disease in Childhood.

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