John H. Davis, Chronicler of Kennedys and Others, Dies at 82 John H. Davis, a prolific chronicler of prominent American families including the Kennedys, the Guggenheims, the Gambinos and the family he shared with his cousin, Jacqueline Kennedy Onassis - the Bouviers of New York and East Hampton - died on Jan. 29 at his home in Manhattan. The cause was complications of Alzheimer's disease, said his sister, Maude S. Davis. Mr. Davis wrote eight books, beginning in 1969 with "The Bouviers: Portrait of an American Family," a brisk seller that boded well for his future in the book trade but left relations with his cousins Jackie and Lee Radziwill, her sister, strained. Another bestseller in 1984, the 900-page "The Kennedys: Dynasty and Disaster," which offered an unflattering view of family dynamics, ended any further contact between them. It included a rehash of the Chappaquiddick episode, in which a young woman drowned when Edward M. Kennedy drove his car off a bridge on an island near Martha's Vineyard, and a painfully close-up view of the 1984 drug overdose death of Robert Kennedy's son David. "After "84, Jackie made it pretty clear she didn't want my brother's company," Ms. Davis said. It's kind of too bad; they had a lot in common. My brother was a writer at heart, as was she. But she was about family myths, and John tried very hard to write truthfully. In the 1980s and "90s, Mr. Davis's ability to recollect childhood summers spent with the former first lady at their grandfather's estate on Long Island, and his doggedness as a researcher and writer of popular history about the Bouvier and Kennedy families, made him a regular on television programs like "The Today Show," "Larry King Live" and "Geraldo" whenever the subject was Ms. Onassis, which was often. Unlike most authors who wrote about her, Mr. Davis brought an eyewitness's view to the family history. In his first book, he debunked the Bouviers" longstanding claim to noble ancestry, tracing their lineage to a foot soldier in Napoleon's army who came to America in 1817, built cabinets and amassed a fortune through investments. He offered up-close views of painfully intimate moments: the chilly first meetings between the two society families, as the Bouviers realized they were poor relations in comparison with the Kennedys; Jacqueline's wedding day, when her rakish father, John Bouvier, sometimes called Black Jack, became too drunk to escort her down the aisle, according to Mr. Davis; Jacqueline's composure in insisting on a full-fledged children's birthday party at the White House on Nov. 25, 1963, for John F. Kennedy Jr., who turned 3 that day, the day of his father's funeral. Another first cousin, Edie Bouvier Beale, a socialite whose later, addled life was recorded in the 1975 documentary "Grey Gardens," gave Mr. Davis one of his most singular critiques. "Oh yes, we're all descended from 14th-century kings," she told New York magazine in 1972. Now a relative has written a book saying it's all a lie. She added: "He's a professor, John H. Davis, and he's breaking with history. Everyone is. That's how I know the millennium is coming. The Bouviers: Portrait of an American Family. Not a bad book really. John Hagy Davis was born June 14, 1929, in Manhattan, the son of John E. Davis, a stockbroker, and Maude Bouvier Davis. He attended private schools, graduated from Princeton and served in the Navy from 1951 to 1953. Through the 1950s and "60s, he studied and taught Italian history and literature at schools in Naples, Italy. A marriage ended in divorce in the early 1970s. His sister is his only immediate survivor. Mr. Davis wrote a well-received book in 1978 about another family, "The Guggenheims: An American Epic." He also entered the thicket of Kennedy assassination literature in 1988, with "Mafia Kingfish: Carlos Marcello and the Assassination of John F. Kennedy." That led to "Mafia Dynasty: the Rise and Fall of the Gambino Crime Family," his last book, published in 1994. "Kingfish" was one of scores of books written in the wake of the three-year investigation by the House Select Committee on Assassinations, which concluded in 1979 that Lee Harvey Oswald was most likely part of a conspiracy to kill the president, contrary to the findings of the Warren Commission, which said he was a lone assassin. Mr. Davis followed the committee's lead in suggesting that Mr. Marcello, a New Orleans crime boss who had been vigorously pursued by Attorney General Robert F. Kennedy, was involved in that conspiracy. He underlined links between Mr. Marcello, Mr. Oswald and Jack Ruby, the Dallas nightclub owner who killed Oswald. "I think John wrote one of the best books on this theory," said G. Robert Blakey, who was chief counsel to the House committee and now teaches law at the University of Notre Dame. And I don't just say that because I happen to agree with his theory. Mr. Davis's reputation among some writers and assassination investigators as a dilettante was ill-deserved, Mr. Blakey added. "He did his homework," he said. Ms. Davis said her brother had wanted desperately to know Ms. Onassis's views on the subject. But, she said, he never had a chance to ask.