Tony Oppedisano doesn’t believe Frank Sinatra was the biological father of Ronan Farrow.

The late singer’s pal wrote a memoir titled "Sinatra and Me: In the Wee Small Hours," which was released on Tuesday.

In an excerpt obtained by People magazine, Oppedisano addressed Sinatra’s friendship with Mia Farrow after their marriage ended in 1968. He acknowledged the ongoing rumor that Sinatra could have been Ronan's father.

That theory made headlines in 2013 when Farrow was asked by Vanity Fair if Sinatra could have been her son’s father. Her response was "possibly."

But Oppedisano isn’t buying it.

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Tony Oppedisano doesn’t believe Frank Sinatra was the biological father of Ronan Farrow.

Tony Oppedisano doesn’t believe Frank Sinatra was the biological father of Ronan Farrow. (Getty Images)

"There’s been a lot of gossip about Frank possibly being Ronan’s biological father," he wrote, as quoted by People. "Rumors I believe I’m in a position to tamp down."

He alleged that Sinatra’s health issues would have made it nearly impossible. He pointed out that in late 1986, Sinatra had emergency diverticulitis, which caused him "to wear a colostomy bag until he fully recovered."

Ronan was born on December 19, 1987.

"There are only two ways Frank could have fathered Ronan, both absurd," he wrote. "Either Mia made a secret trip to shack up with Frank in his California home with [fourth wife] Barbara present, or Frank, wearing his always romantic colostomy bag, made a quick trip to Connecticut between his Atlantic City performances."

"If Ronan had been Frank’s son, Frank would have acknowledged him," Oppedisano added.

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American singer Frank Sinatra (1915 - 1998) stands with his arm around his third wife, actor Mia Farrow, during their private wedding in Las Vegas, Nevada. 

American singer Frank Sinatra (1915 - 1998) stands with his arm around his third wife, actor Mia Farrow, during their private wedding in Las Vegas, Nevada.  (Photo by Hulton Archive/Getty Images)

As for the physical resemblance between the two, the author isn’t fazed by that either.

"People say, ‘Take a look at [Ronan]’ and I say, ‘Well, take a look at Mia at the same age,’" he wrote. "They look like twins. I’ve got blue eyes too and I’m not Frank’s son."

Still, Oppedisano noted that Sinatra and Farrow remained friends, alleging he arranged a private visit in 1992 between the two at the Waldorf Astoria.

"When she was beginning to have problems with Woody [Allen] she was looking for some comfort and it was like two old friends catching up," he said. "She was devastated and he was there to support her."

In 2013, Ronan described the rumor as "hilarious."

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Ronan Farrow previously called the theory "hilarious."

Ronan Farrow previously called the theory "hilarious." (Reuters)

"You know, that story has been out there for years," the 33-year-old told Vulture at the time. "It was somewhat surprising to see it break in such a huge way of late… I appreciate how hilarious it is."

"I mean, it’s a ridiculous situation," he continued. "That said, I’m pretty unfazed by it in substance because it’s been out there both publicly and privately for so long. I have a relationship that I’m very happy with, you know, with all parties involved. For me, the imperative is, all right, we’ve talked about it, I get a kick out of it, everyone gets a kick out of it."

Woody Allen also cast some doubt in the theory.

"In my opinion, he’s my child," the 85-year-old told New York Magazine in 2018. "I think he is, but I wouldn’t bet my life on it."

Sinatra passed away in 1998 at age 82.