When Joe Lieberman was a young boy living under his grandmother's roof, he shared a bedroom for a time with his Uncle Benny. The pair remained close even as Lieberman grew into adulthood and became a U.S. senator, so it was no surprise that Bernard Manger, who had started a prosperous electronics business out of his grandmother's Stamford, Conn., garage, turned to his nephew to be executor of his estate.

But when Manger tumbled down a flight of stairs five years ago and died, the will he left behind cast Lieberman in an agonizing role.

Manger, renowned for his charity, had disinherited from his $48.2 million estate two of his own four children, who had married outside the Jewish faith. What's more, the will directed the senator to ensure that his cousins lived by certain rules his uncle prescribed: Work hard, refrain from drugs, and cling to Jewish observances.

How Lieberman sorted through his obligations--to the uncle he admired and to the rest of his family--was in microcosm a test he now faces as the Democratic candidate for vice president: How to remain loyal to his Orthodox Judaism without seeming dogmatic or exclusionary.

For Lieberman, the discovery of the will's contents "was terrible," recalled Elizabeth Haas, the senator's first wife, who has remained on friendly terms with Lieberman and who attended Manger's funeral. "I know he was upset."

Within a matter of months, according to a friend and adviser to Lieberman, the senator found a solution. It came in the form of a later will, found unsigned and lying among Manger's papers, that appeared to indicate his uncle had begun shortly before his death to consider ways that all his children might share in his wealth.

At Lieberman's request, the probate court in Stamford modified the will. The two disinherited children would receive an annual payment and housing allowance from the estate. In turn, their spouses, who already had converted to a less strict form of Judaism, underwent an Orthodox conversion. Their children, they promised, would be bar mitzvahed.

Yesterday, as Lieberman's staff scrambled to explain his role with the will, first reported in the Wall Street Journal, a campaign spokeswoman called it "a surprising and complicated family situation." The spokeswoman, Kiki McLean, said the senator has made plain in the intervening years that "the decisions his uncle made are not decisions he would make in his own family."

Perhaps not entirely, but over the years Lieberman has emphasized in his own family that preserving the faith is a matter to be taken seriously.

When his two children from his first marriage became teenagers, Lieberman made clear they should date only Jews, said Haas, his ex-wife who separated from him in 1981 and had joint custody of their children.

When his son, Matthew, met the woman he would marry, April, who was not Jewish at the time, they remained merely friends for years. Only after she converted to Judaism by Orthodox standards did Matthew begin to date her. Lieberman's daughter, Rebecca, also "does not date non-Jews, as far as we know," Haas said.

And yet, Lieberman's sister married a man who was not Jewish and has not converted. "The family was not happy about it, but his reaction was, 'She's my sister, and I love her,' Haas said.

Manger, 22 years older than his nephew, had a less tolerant view. Paradoxically, "he was not devout. He was not like Joe Lieberman," said Joseph Ehrenkranz, a rabbi emeritus in Stamford who was the senator's childhood rabbi and knew Manger well. But having watched the extermination of Jews during World War II, Manger vehemently objected to "the possible assimilation of the Jewish faith and the Jewish people," said Judith Bragin, a cousin of Leiberman and Manger's niece.

When Manger died in May 1995, the family was stunned by the size of his estate. Bragin said he had spoken to her about his desire to disinherit his eldest daughter, Joyce Maskart, of Seattle, and one of his sons, Marc Manger, who worked in the family electronics business until earlier this year.

The friend of Lieberman's, who asked not to be identified, said the senator had told him he was "shocked and surprised" that the will excluded two of his first cousins. Using the later, unsigned will as evidence of his uncle's true intent, he persuaded the probate court to include them before the end of 1995.

Lieberman also asked a second cousin, a Stamford lawyer named Harold Bernstein, to be co-executor of the estate. Lieberman and several other relatives received an initial $25,000 from the estate. The will allotted him an additional $50,000 per year, although the senator has accepted a yearly amount of $20,000, according to the friend, who said his wife, Hadassah, is paid an additional $40,000 per year to help manage the trust of Manger's widow.

As for the instructions that he enforce his cousins' behavior, relatives say Lieberman has taken a relatively unintrusive role. But Bragin said, "Joe knows [his uncle's] children and sees them very frequently . . . so I suspect he knows they're fulfilling the requirements of my uncle's will."