The members of the small group have a common bond. All of them are parents who have lost a child to death.

Some of the young victims committed suicide. Some died in accidents. Others died after months of fighting incurable illnesses.

Once a month the Parents United by Tragedy get together for 90 minutes or so at Congregation Solel in surburban Highland Park. They tell their personal stories. They give each other emotional support. At the end of the meeting they join hands and participate in a moment of silent prayer.

The leader of the group, which includes blacks and whites, Jews, Christians and nonbelievers, is Rabbi Robert J. Marx, spiritual leader of the reform synagogue since 1973.

When he talks about how it feels to be the parent of a child who has died, the 50-year-old rabbi speaks with authority. In 1973, David, one of the rabbi's two sons, died at the age of 15 after prolonged suffering.

"The formation of the group just sort of happened," Marx said last week. "I found I could help people who had lost a child. In that sense, my loss was a gain. People were coming to me for counseling from all over the city.

"When I was in the midst of my deepest grief," he recalled, "the thing that helped the least was the comment of people who said, 'I know how you feel,' but who obviously didn't know. What helped the most were the words and the presence of those who had been through the same experience. This was of immeasurable value." In the study of his home near Lake Michigan, Marx spoke with quiet deliberateness about David's long illness, his death and the sense of loss he left behind.

"When I first heard the diagnosis, my instictive reaction was to say, "We've got to find a cure for it," Marx said. "One of the heritages of our scientific age is that we expect that some medicine will be available that will produce a miracle. This is one of our ways of blotting out the reality of what is happening.

"My next reaction was a desire to take away the pain myself. I had this feeling that I wanted to spread myself over his pain-racked body and say, 'David, I'm going to take on the pain so you won't have to suffer.' If I could have done this, it would have been easier than watching him die.

"For a long time, David's illness became a way of life for me. When someone said, 'Don't you want this to end?' I felt like screaming a 'no' at them. Being with David, doing the little rituals that made him more comfortable, became more precious than anything else."

The day of David's death remains vivid in Marx's memory. He recalls the desire of the hospital nurses to withhold the news from him, and their inability to look im in the face.

He also recalls an unpleasant moment in the lobby of the New York apartment building where he was living. "The elevator was slow in coming. A woman, another resident, complained, 'Isn't this elevator just awful? This is something I just can't stand.' She went on and on. Meanwhile. I was standing there holding a little bundle containing my dead child's clothing and a football Joe Namath had given him.

Marx has come out of the experience reinforced in his conviction that people must have multiple sources of meaning for their lives.

"Sometimes I get the feeling," he said, "that some people put too much into their families. It's terribly important not to invest everything in one place. When one support system fails, we need others that enable us to go on."