Actress Mia Farrow has admitted that her biological son with Woody Allen could "possibly" have been fathered by her former husband Frank Sinatra.
Vanity Fair magazine spoke to the Rosemary's Baby star and eight of her 14 adopted and biological children for its November issue.
During the interview Farrow said Sinatra was the great love of her life and added: "We never really split up."
But added that a DNA test had never been carried out on 25-year-old Ronan.
As the claims made in the interview emerged, Ronan tweeted: "Listen, we're all *possibly* Frank Sinatra's son."
Vanity Fair's correspondent also spoke to Nancy Sinatra Jr about Ronan and she reportedly replied in an email: "He is a big part of us, and we are blessed to have him in our lives."
A representative for Allen told the Associated Press: "The article is so fictitious and extravagantly absurd that he is not going to comment."
Farrow was married to Sinatra from 1966 to 1968 but their relationship continued afterwards, including during the early years of her relationship with the award-winning director, which began in 1980.
Ronan was five when his parents split in 1991 following Allen's much-publicised affair with 19-year-old Soon-Yi Previn, Farrow's adopted daughter from her marriage to Andre Previn.
Allen, now 77, and Soon-Yi married in 1997 and have two adopted teenage daughters.
Farrow has largely given up acting and now concentrates on human rights campaigning and her role as a Unicef ambassador.
Frank Sinatra died aged 82 in 1998.