The Soviet Union indicated today it will not allow a youth who lived for several years with the family of dissident figure Alexander Ginzburg to accompany them to the United States as part of a prisoner exchange deal.

Tass, the official news agency, in a dispatch that for the first time officially mentioned the month-old swap, called Sergei Shibayev a "pseudo-son" of Ginzburg. The family has sought to have Shibayev, a Red Army draftee included as a close family member and given an exist visa along with Ginzburg's mother, wife and two sons.

Tass said Shibayev "has parents who strongly object to their son's departure aboard . . . . Hence it is not a question of reunion of a mythical family, but of attempts to break up a real family."

The Ginzburgs took Shibayev, 19, into their family nearly seven years ago. They say they did so out of compassion for the youth, whose mother they described as a "pathological alcoholic." Shihayev was drafted in 1978, although he suffers from a leg deformity as the result of a childhood disease.

Ginzburg'st wife, Arina, has said she will not leave the Soviet Union unless Shibayver is allowed to leave. She says she fears that because he has lived with the Ginzburgs, he will suffer reprisals from the authorities after they leave.

Ginzburg and dissidents Georgyi Vins, Eduard Kuznetsov, Mark Dymshits and Valentin Moroz were traded April 27 for convicted spies Rudolf Cheryayev and Valdik Enger.

The Tass account does not categorically rule out emigration for Shibayev, but leave little doubt that authorities will not allow him automatically to included. But Tass reported that the Soviet have expanded their definition of "immediate family" to include a niece of Baptist dissident Vins.

"Nephews and nieces do not belong among close relatives," Tass said, "Nevertheless, competent authorities found it possible to grant permission to Vins' niece, L. Glukhoman, to leave the country to join her uncle."

The U.S. Embassy, which is aiding the families in their departure efforts, said no U.S. visas have been issued to any family members. It could not be determined here whether the United States, in the six months of negotiations to arrange the exchange of the dissidents for the spies, had taken any position on whether Shibayev was to be considered a member of the Ginzbury family for purposes of the swap.

Embassy sources said today that U.S. diplomats have spoken on behalf of the Ginzburg's request to the Foreign Ministy, but have received no reply. The embassy apparently has not formally supported the request, as a matter of diplomatic courtesty between the countries.

Tass did not mention that the five dissidents were exchange for the two Soviet former @u.n. employes, who had been convicted of spying by a U.S. court, but said only that "Soviet authorities decided some time ago to expel from the U.S.S.R. Ginzburg, Vins and a number of other persons engaged in anticonstitutional activities or [who have] committed grave crimes."