EXCLUSIVE DETAILS: The last of the BOUVIER men, best-selling author JOHN H. DAVIS, Jackie Kennedy’s beloved first cousin, has died at 82.

Davis who not only wrote a number of bestselling books about The Bouviers, Kennedys and a lengthy tome about Jacqueline Bouvier Kennedy died from advanced Alzheimer’s on Sunday, his sister, Maude Sergeant Davis, confirmed.

Davis was 82 and the last of the Bouvier men.

Davis and his sister, 77, were the children of Maude R. Bouvier Davis, the sister of John Vernon (Black Jack) Bouvier who was the father of Jackie and sister Lee Radziwell.

Davis attended Princeton and served as a naval officer with the Sixth Fleet in the Mediterranean.  He was living in Naples, Italy, and running the Tufts University’s American Studies Center in the 1960s when his mother contacted him.

“My mother heard that someone was writing a book on Bouviers and she told him to come home now,” she recalls. “She said, ‘I’ve got the material for this book, and no one else is going to write it.’

“He just really needed to get his teeth into something. So he did it,” she said.  In 1969, Davis published “The Bouviers: Portrait of An American Family.”

The publication led to a riff in the family leading John to be ostracized as the black sheep of the Bouvier clan.

A long time regular at Greenwich Village's artists and writers bar, The Cedar Tavern, Davis held court with tales of the Kennedys, the Bouviers and the mob (including a best seller on John Gotti “Mafia Dynasty”).

He long maintained that JFK was assassinated by  New Orleans mob kingpin Carlos Marcello in his books “Mafia Kingfish” and “The Kennedy Contract”. Marcello ordered the hit after Attorney General Bobby Kennedy led a vendetta against the crime boss.

Fueled by booze and an aristocratic ideal, he spoke often about his banishment from Camelot, the Bouviers and from his cousin Jackie.  He openly wept  when she died.

Their estrangement was caused by the publication of “The Bouviers” as Jackie didn’t approve of Davis’ depiction (albeit accurate) of her father as a boozing womanizing blackguard.

“He felt increasingly like an outsider, and that was hard on him," his sister said.

The craggy jawed Davis who was ruggedly handsome in his youth, had obviously identified with the bawdy Bouvier men, his sister said. "He wanted to pattern himself after Black Jack," she added, saying Davis' depiction of Jackie's father "(was) very sympathetic to him."

John was also a longtime friend to The ENQUIRER — and to this author — as we enjoyed many a night at Cedar reveling in his colorful tales of life, love, the arts.

The light is now forever dimmed at John’s long-time 20 East Tenth Street floor through in the Village – the one-time prodigal son forever banished.

When Jackie died, John spoke of Jackie's bravery in the face of tragedy. He told this author through sobs, “She was truly gallant.”

As was John H. Davis.

You WILL be missed, sir.