Although no DNA tests were ever done, Ronan, a 25-year-old former Rhodes scholar who bears a striking resemblance to Ol' Blue Eyes, remains close to the late crooner's family, as does Farrow, Vanity Fair reports in its November issue, in an interview with the actress.
Farrow, 68, who was married to Sinatra from 1966 to 1968, admittedly continued a relationship with the music legend while she was involved in a longtime relationship with filmmaker Allen.
Sinatra, who died in 1998, would have been about 72 when Ronan, born in 1987, was conceived.
Asked point blank by Vanity Fair's Maureen Orth whether Ronan could be Sinatra's son, Farrow responds with one word: "Possibly."
According to the article, the Sinatra family remains a fan of Ronan, a Bard College and Yale Law School grad who has served in the Obama administration, founding the State Department's Office of Global Youth Issues.
"He's a big part of us, and we are blessed to have him in our lives," says Frank's daughter, Nancy Sinatra, 68.
Farrow also acknowledges the families remain close. When Sinatra died, she and Ronan attended his funeral together. "We are family and will always be," Farrow, a mother of 15 children, many with special needs, tells the magazine.
In the article, she also discusses the scandal behind her split with Allen, now 77, and the sexual abuse case involving her adopted daughter Dylan.
Allen, through his lawyers, continues to deny the allegations.
Since 1992 he has been married to Farrow's estranged daughter, and Ronan's sister, the former Soon-Yi Previn, who turns 40 next week.
Listen, we're all *possibly* Frank Sinatra's son.— Ronan Farrow (@RonanFarrow) October 2, 2013