Tina Sinatra, the legendary singer's youngest daughter recently revealed in an interview with Showbiz 411, that her father had a vasectomy some time before Ronan was born, so there is no way he could be his biological parent.
Confirmation as to who fathered Ronan has never emerged as Farrow has evaded the question in interviews for many years. So much so, that it has almost become a bit of a joke amongst the family.
Farrow married Sinatra in 1966 but the marriage only lasted 18 months before it broke down due to a dispute over Farrow's acting role choices. It is said that the singer wanted his wife to star alongside him in The Detective but she opted to play the mother of the Devil in the iconic film that undoubtedly made her name. The couple divorced in 1968, the year both films were released.
Farrow, 70, said that her and crooner Sinatra "never really split up" and he was the love of her life, which could throw some light on the fact that she claims they could have a child together, despite Ronan being born almost a decade after their divorce.
At the time of Ronan's birth, the Rosemary's Baby actress was actually in a long-term relationship with Woody Allen, so since Ronan's birth he has been marked as another potential father.
The film icons met in 1980 and were together for 12 years before it ended due to the discovery that Allen was having an affair with Soon-Yi Previn (Farrow's eldest adopted child from her previous marriage to pianist Andre Previn).
The revelation that Allen is now most likely his father will undoubtedly be less-than-joyous news to Ronan, who had a documented falling-out with the director after his affair became public. "I cannot see him. I cannot have a relationship with my father and be morally consistent" stated Ronan. "He's my father and married to my sister. That makes me his son and his brother-in-law. That is such a moral transgression."
HBO will air a documentary about Sinatra, All Or Nothing At All, this Easter Weekend which is said to go into depths about his tumultuous relationships and Farrow is bound to be a focal point. The programme will air 5 Sunday and 6 Monday at 8 ET/PT.