Could Frank Sinatra be Ronan Farrow’s dad? A Sinatra buddy (and biographer) says no

Frank Sinatra’s newest biographer says the late singer can’t be Ronan Farrow’s biological father because former spouses Sinatra and Mia Farrow couldn’t have worked out the logistics around the time of conception.

“Over the years, there’s been a lot of gossip about Frank’s possibly being Ronan’s secret biological father — rumors that I believe I’m in a position to tamp down, if not put to rest,� Tony Oppedisano writes in “Sinatra and Me: In the Wee Small Hours,� which came out Tuesday.

Ronan Farrow was born Satchel Ronan O’Sullivan Farrow in December 1987, more than 20 years after Ol’ Blue Eyes served the actress with divorce papers to end their 16-month marriage. From 1980 to 1992, Mia Farrow was in a relationship with Woody Allen, Ronan Farrow’s legal father. Farrow and Allen split after the director pursued a relationship with stepdaughter Soon-Yi Previn.

But there has been buzz over the years that Ronan was really Frank’s son, as Sinatra and Mia Farrow continued their friendship long after their split. Also, Ronan, now an award-winning journalist, has the same bright blue eyes as the singer — and the actress.

Oppedisano, who became Sinatra’s pal in his early 20s and was later his best friend and road manager, said the artist had emergency diverticulitis surgery in late `1986 and was left wearing a colostomy bag during recovery. That bag was replaced by another, he writes, after another hospitalization in February 1987.

By the author’s calculations, conception would have had to take place between March and early April 1987. Sinatra, however, was at home with fourth wife Barbara, recovering, all during that time, with the exception of a short trip to Vegas for shows April 3-6. Then, with Barbara, he went on a tour that started April 12 and included shows in Chicago, Boston and Atlantic City, N.J.

“Throughout this time, Frank had to continue wearing the colostomy bag,� Oppedisano writes. “As for Mia, throughout March and April of 1987, she was shooting a movie called ‘September’ that Woody was directing on location at their home in Connecticut.�

“September� came out Dec. 18, 1987, a day before Ronan Farrow was born.

Oppedisano posits only two ways the former spouses could have connected during that period: “Either Mia made a secret trip to shack up with Frank in his California home with Barbara present, or Frank, wearing his always romantic colostomy bag, made a quick secret trip to Connecticut between his Atlantic City performances to rendezvous with Mia.�

He holds out one final observation: “If Ronan had been Frank’s son, Frank would have acknowledged him. There’s no way he would have denied Ronan if there’d been any possibility Ronan was his. Frank adored his children, all of them.�

That said, Oppedisano later noted a meeting he says he arranged between Mia Farrow and Sinatra in 1992, when he created a diversion so the security team wouldn’t be able to tell Barbara Sinatra about their hotel-room interaction. Despite their split, Mia Farrow and Sinatra remained friends until the singer’s death.

“[W]hen the news of Woody Allen’s sexual relationship with his stepdaughter hit the news,� Oppedisano writes, “Frank immediately reached out to Mia to offer his support, whether it be financial assistance or a sympathetic ear.�

Meanwhile, Mia Farrow told Vanity Fair in 2013 that Ronan was “possibly� Sinatra’s son and that Sinatra was the great love of her life. Ronan Farrow attended the singer’s funeral in 1998 with his mother.

“He is a big part of us, and we are blessed to have him in our lives,� Frank Sinatra’s daughter Nancy Sinatra said of Ronan Farrow in that same article, adding that she and Mia Farrow “have been like sisters. ... We are family and will always be.�