He prefers hang gliding to international intrigue. "I'm not very political," says Alexei Semyenov, stepson of leading Soviet dissident Andrei Sakharov. He was reared on anti-Soviet dinner table discussions and kid games included matching wits in the streets of Moscow with the KGB, but now he is forced into playing politics on a grand scale.

Semyenov lights a Marlboro 100 with a kitchen match and mumbles his disdain for the sudden burst of media attention. All week, a parade of reporters has kept him hopping from phone to front door, from television studios to press conferences.

Yet he seems comfortable with it. At times, even polished. And why not? His childhood, after all, was spent in the Soviet fishbowl, and he has been grilled by some of the world's sharpest questioners: the Soviet secret police.

"No, I don't like all this attention," Semyenov says quietly. A pair of French journalists wait their turn in the next room. Outside, a television crew is tramping through the snow. And the telephone rings nonstop. "But I knew I had to use the media, that this was very important to my parents' survival."

For a time, he was willing to concede he would never again see his wife-by-proxy Liza Alexeyeva; the 17-day hunger strike begun on Nov. 22 by Nobel laureate Sakharov and his mother, Yelena G. Bonner, to pressure Soviet authorities into allowing Alexeyeva to emigrate to the United States had been a tragic political miscalculation.

"Tuesday was the most terrible day of all," he says, lighting another Marlboro. Several open packs are scattered on the floor, ashtrays overflowing. "I actually thought my parents were dead." But by the weekend, it appeared that all the interviews Semyenov had given had succeeded. Alexeyeva was granted a visa. And yesterday, the Sakharovs, who ended their fast last week, were reported in good condition.

Still, Semyenov, a lanky 25-year-old graduate student who has been studying mathematics at Brandeis University in nearby Waltham since arriving here in 1978, continues to talk to reporters. "We have to keep the pressure on," he says.

Semyenov lives on Maplewood Street in a large white house with gray shutters in this mostly Jewish, mostly liberal suburban neighborhood. He lives with his grandmother, his sister and her husband and their two children, all of whom emigrated here shortly before he did. When Liza arrives from Russia, in perhaps two weeks, she will live here, too, Semyenov says. And after that? "Maybe a job with Bell Laboratories. It's hard even to imagine that I should think about the future. None of this seems real yet."

There are few signs of the reality he left in Russia: a tiny sticker on the back window of the family's banged-up blue Chevy Citation that says, "Release Andrei Sakharov." And inside, piles of newspaper clippings, an assortment of typewriters and an Olivetti copy machine to aid in communications with the dissident movement back in the Soviet Union.

And, oh yes, one very vivid reminder of back home: a phone call just one week ago as the drama was unfolding. "A man's voice said, 'If Sakharov dies we'll get you.' I had heard that tone of voice all the time when I was growing up. It wasn't what he said, so much. But the tone was the KGB. They like to do that," says Semyenov.

He was born in Leningrad. His father, a physician, still lives there. "He doesn't like the dissident connection," says Semyenov. His mother, a pediatrician deeply involved with members of the Russian intelligentsia, left her husband when Semyenov was 6, and the two moved to Moscow. Shortly after the Russian invasion of Czechoslovakia in 1968 she met Sakharov, already a prominent champion of civil rights, through mutual friends. They were married soon after.

"I was brought up in an atmosphere that didn't believe in restrictions or anti-Semitism," Semyenov says. "I would pick up books at home that were considered criminal, that you could get seven years in a labor camp for reading: poets like Mandelchtam, who died in a labor camp in 1937, or Orwell's '1984.' "

And always, says Semyenov, there were threats from the Soviet secret police. "The KGB followed me everywhere. They would come up to me and say, 'We're going to get you, we're going to kill you.' And we knew they listened to our telephone all the time because sometimes they would make a mistake and we would hear our own conversations being played back on the tape recorder through the telephone."

Semyenov breaks into a mischievous grin. He was something of a wise guy, he says. "The threats didn't mean anything to me. I was a kid. I was foolish. I would laugh at them." And he tells of mocking the KGB. "I was lookng for a taxicab one day and I couldn't find one." So he hailed the KGB car following him. "There were three of them and I asked if they had room for one more, and could I have a lift?"

Semyenov was the beneficiary of twisted secret police logic, he says. "They pressured me but they also protected me. I could get away with more things than my classmates. I had more freedom because they figured I was already a dissident, I was from a dissident family, and it didn't matter what I did. They thought, 'So what?' " And in school? "The teachers avoided sharp discussions with me because they knew I would answer not in a manner of a good Soviet citizen.

"I didn't feel compelled to be cautious," he says. "I was already marked, so I could be offensive. I always felt I could tell whatever I think. My parents thought I acted stupidly. They were much more nervous than I was. After all, it was all aimed at them."

Semyenov says he was cast in the role of "the kid" of the dissident movement. "They treated me that way. And I never really thought about it. I had no desire to be active politically. It was all around me anyway -- the discussions, the literature. I just didn't feel the need to get involved."

But in 1976 his sister was hit with serious political charges and forced to emigrate. And soon after, he too was pressured by Soviet authorities. He was expelled from Moscow's state pedagogical institute shortly before graduation. "And they told me I would be forced to join the army, where I would be sent to a place worse than a labor camp." Unless he chose to leave the country.

In an unusual display of bureaucratic haste, Semyenov was granted an exit visa just one day after applying, he says. "They were trying to isolate my parents, to create an absolute vacuum by getting rid of the rest of the family."

But if Soviet authorities wanted to break all family ties to the Sakharovs, then why prevent Semyenov's wife from leaving Russia? "It is difficult to figure out the logic of the KGB," says Semyenov. "But at least they have ultimately decided to allow Liza to leave."

Semyenov met her while the two were studying mathematics during college. He had been married at the age of 18 to another woman, Olga Levshina. They separated after two years. "It was very hard on her, my connection with the dissidents. She would have liked me to not associate with the movement." Levshina and their child emigrated to the United States shortly after Semyenov received a divorce in Massachusetts probate court last year. His marriage to Alexeyeva was conducted by proxy in Montana, the only state other than Nevada that allows proxy weddings.

Now Semyenov is just marking the days, waiting for life to take another spin. He appears thoroughly Americanized: jogging shoes, designer jeans, tinted glasses. And like other New Englanders, he summers on Cape Cod and hikes through the white mountains of New Hampshire in the fall. And, of course, there is hang gliding. "It is my passion," he smiles.

As for his parents: "I don't believe they will ever let them out of the country. They are virtually under arrest right now. And I believe they will put even more restrictions on them. I think they will be shut off completely from the outside world. Unless there is pressure from the West. Constant pressure."