Q. "My sons, 13 and 15, are both fine, intelligent children, but they are exact opposites: dark and fair; optimistic and pessimistic; outgoing and inward.

"When they were little they were pretty close and everyone commented that 'opposites attract,' but as they got to pre-adolesence they began to fight a lot, although they still laughed and roughhoused, too.

"Now they just stay to themselves, sometimes for days at a time, barely speaking. This is the doing of the older child -- the one who is fair, pessimistic and inward. He's usually pleasant to others, but not to his little brother. It's worse when his friends are visiting.

"The younger one seems so anxious when his big brother is around, which worries me. It's not in his nature to be like that.

"My husband thinks I'm just looking for something to worry about. Am I?"

A. No.

It's true that occasionally two children in the same family will have such different chemistry that they go their separate ways, but they still should get along reasonably well -- the way your boys used to operate together -- and they still should show some affection.

They will, of course, show it in strange ways, for sibling rivalry is a part of every sibling. There will be arguments when one of them is bored, or because their interests and their ages are different, or because one of them is mad at his best friend and takes it out on his brother, or perhaps because the moon is full . . . who knows?

That's fine, if it goes no further.

A family is the one safe place a child can explode, and he does it in a number of ways.

Unfortunately, your older child has found a poor solution. It's all right to seek privacy, but to demand isolation -- and to enforce it on others -- is not. If unchecked, you will see your older child become more and more of a loner, and that's one of the worst things that can happen.

For some reason he is hurt, and this isolation is a symptom.

The hurt probably began in early adolescence: the typical time for self-esteem to plummet. At his age a child thinks the world will open up for him, but instead he is often embarrassed by the awkward things he says and does and spends hours brooding about them.

Now he sees his little brother start adolescence and every gaffe he makes becomes a reflection of himself, as if the younger child had no identity of his own.

Just as a family is the place for a child to learn how to deal with his anger, so it is the place to learn how to handle other emotions. Here is where love is expressed -- or not expressed -- and dreams are shared. The child who keeps anger to himself will keep joys inside too, so he always will hold people at a distance.

He also will miss one of life's fine experiences -- the friendship of a brother.

We think you should confront this directly, privately, quietly -- holding hands -- as you ask your older child what hurts so much. He'll tell you all the rotten things his brother does to annoy him, and you'll just listen, but sooner or later he'll say how embarrassed he gets and bit by bit you'll hear about his own inner agonies.

It will take a few of these talks, and some with the younger child, too. And then some family talks together, so everyone can put his anger out on the table and dispose of it.

And if there is still too much tension for you and your husband to handle, we'd recommend a few family therapy sessions, and perhaps some individual sessions for your older child to help him find his strengths. Once he knows how special he is, he can accept his little brother again. You can't give your boys a better legacy than the friendship of each other.