Recently I was asked by someone who did not know my family what my brother Roger did for a living, and I started to reply that the was retarded. Suddenly it struck me, for the first time in the 28 years of our relationship, that mental slowness is not the sum of his existence.

He is also a person who is married, holds down a part-time job, and has learned how to limit the amount of information he receives so that he is not overwhelmed.

What he does for a living, in fact, is not to act retarded, but to work in a fast-food shop.

I replied that my brother was in the restaurant business."

It's inevitable that a retarded person will have a significant impact on his family," said Michael J. Begab, head of the Mental Retardation Research Centers branch of the National Institute of Health.

"What that impact is depends on the family, and how well it handles stress . . . It can enrich lives, or confuse them, but it is too significant an event not to have an impact at all," he said.

Roger and I took trips together, went to the movies together, played together, and always I slowed my own responses so that I would not outdistance him in appreciation.

I came home from sandlot baseball games early, often for no other reason than just to be around in case my parents, especially my mother, needed "help" with him. I think that "help" was simply my presence, reassuring them that their world was not totally filled with intelligence testing and reading difficulties.

There was a tremendous burden on me not to raise hell, not to disturb their already disturbed lives. I have never felt resentment towards my brother, but often when I wanted to yell at my parents for slights - real or imagined - I kept my anger to myself.

What made matters worse was that my father called me his "good right arm," my mother said I was "like a second father" to Roger, and Roger himself often called me "Dad" before he switched titles in mid-breath and called me "Bobby." All of this was a heavy load for someone entering early manhood.

My parents realized the dual roles I was in, and tried to compensate. They moved from one neighborhood to another so I could attend a better public high school. They paid for my five summers in a Vermont summer camp, and then they paid a fee that allowed me to apprentice at a summer stock theater.

Worried about my ways as a loner in high school, mother insisted I invite all the "better" sort of kids from high school to our apartment, as a way of getting me into a more active social life. I went ahead with the idea because I was a dutiful son. At the party I was the only one without a date.

I wasn't a bad student in school, but I probably held myself back, so as not embarrass Roger by my academic success.The awful phrase, "could do better," was always checked by teachers making academic evaluations.

I was paricularly embarrassed when Roger started writing poetry, something he told me recently that he did in imitation of me. I was embarrassed because I didn't want him to fail at a craft in which I didn't think he could succeed. But what the has managed to do, with that incredible effort he brought to other aspects of his life, is to carve out for himself a vital form of expression.

In the early days his poetry wasn't very good, but it improved because he worked at it.

I am five years older than Roger, and when we were both teen-agers I always had the sneaking suspicion that our parents did not want to see me grow up. My maturity would have emphasized to them the growing gap between his chronological age and intellectual abilities. It would have raised the question to which they then had no anser - what would happen to Roger when I was grown and they were dead.

There is no objective proof for this belief of mine, and my parents have repeatedly denied that this was their intention. But in the subtle matter of human dynamics, where inflections, sughs, and looks can speak volumes, these were the words I read.

In fact, the changing social attitudes towards the retarded, the availability of state and federal money and support, and most importantly Roger's fierce desire to lead an independent life, have given them the reassurance they sought.

As a result, they have been able to look at each of us with less desperation, with more appreciation of us as individuals. No longer do they see our four-member family as being composed of three equal partners supporting the fourth person.

When my marriage was legally ended two years ago, the support I received from my mother and father was greater than the support I have ever received from them during any other period of my life. Feeling much less burdened by Rogers and what once seemed an insurmountable, insoluable problem, they were able to respond to me as an independent person.

Which is to say the past is prologue, and we can learn from the mistakes. My brother is a man of remarkable dignity, and a great sense of self-worth. He is no more an emotional patsy then I am. In fact, I now recall that when we were teen-agers, he sometimes thought I had pushed him too far, and he responded with a decidedly unbrotherly left cross to the shoulder. His handicaps are serious as he said during our interviews, for this series, but they are not insurmountable.

His new wife, Virginia H. Meyers, herself retarded, also understands her limitationa and potential, and used that knowledge to help others. Her sister, Carol MacIntyre, said that Virginia used to be a particularly sympathetic baby sitter with her young son, Scott, who has cerebral palsy.

"She told me not to worry, that Scottie would learn things, although it would just take him a bit longer, as it did with her," MacIntyre said.

The old response patterns die hard, however. Both our parents worry excessively about Roger. My mother can still be come so tense after a visit to his apartment that she is unable to eat for hours. My father can still rant and rave against the quality of counseling Roger and Virginia receive (though Roger and Virginia do not complain).

There are some new experiences for them, however, some rosier clouds on the horizon. My mother absolutely glowed after receiving a telephone call from her daughter-in-law of one week who began by saying, "Hi, mom."

My father was speechless when I told him how Roger and Virginia, who needed to get a wedding ring tightened during their honeymoon, took it to a jeweler located near their hotel, learned on their own which buses they had to take to pick it up in a week's time. And then picked it up. He was overwhelmed when I told him they had actually returned and picked it up.

And I have learned that my brother and I share certain problems in maintaining an adequate cash flow level. Shortly before returning to Washington after the wedding, I asked my father if I could borrow some money. It turned out Roger had made the same request of him the week before.

"Now both my sons owe me twenty dollars," the old man sighed proudly, forking it over.