IN mob lore, fiction follows fact and vice versa. Otherwise you wouldn’t have a crew of wiseguys saying on secret tapes they were real-life models for “The Sopranos.”

In the case of Charles “Chuckie” O’Brien, he was the real-life model for Tom Hagen, the Irish orphan who was taken in by Don Corleone and later became the family’s consigliere.

Two weeks after the monumental best seller “The Godfather” came out, Mario Puzo told me this in an interview at the Algonquin Hotel:

“Tom is sort of a rough model on a guy called O’Brien in Detroit who was like a son to Jimmy Hoffa,” Puzo told me.

I didn’t know who Charles “Chuckie” O’Brien was at the time, but he was an Irish kid whom Jimmy Hoffa took into the household at the age of 6 after his father died.

In the mob world of double-cross, triple-cross and quadruple-cross, Chuckie O’Brien was high on the FBI’s suspect list after Jimmy Hoffa disappeared on July 30, 1975, outside the Red Fox restaurant in Detroit.

Twenty-six years after the mystery of case number HQ 9-60052 began – and 16,000 leads later – the probe again has refocused on Chuckie O’Brien, whose alibi on the day of Hoffa’s disappearance fell apart like bad clay.

But who could grasp that young Chuckie, a boyhood friend of Jimmy Hoffa’s son, James P. Hoffa – no, more like a brother – could have been the treacherous finger man?

One thing for sure, Chuckie got too close to the real wiseguys.

“Those who know will tell you, the only connection my father had with the Mafia was that he would not let them in, would not let them run the union,” James Hoffa Jr. told me on Nov. 17, 1997.

“And for that he paid the ultimate price.”

The man commonly believed to be the subcontractor in Hoffa’s disappearance was Salvatore Briguglio, a Genovese soldier, who marched to the drumbeat of Anthony Provenzano.

He was so commonly believed to be the subcontractor that he was filled with 12 bullets outside a restaurant on Mulberry Street in March 1978.

Three other hoods were quickly dispatched by hit men within 10 days of Sal’s untimely end.

The man most believed to be the original contractor, Tony Provenzano, took his secrets to the grave when he died of a heart attack in prison on Dec. 12, 1988.

If new evidence throws a net over Chuckie O’Brien, it is hard to grasp that a kid taken from starvation and deprivation by a real-life godfather, in the true sense of the word, would help in his dispatch.

Well, Michael Corleone took out his own brother Fredo.

Fiction follows fact, fact follows fiction.