Frank Sinatra regretted leaving his first wife for Ava Gardner.
The 'My Way' crooner left Nancy - the mother of his children Nancy Jr., Frank Jr. and Tina - in 1951 to strike up a relationship with the actress, and in later years admitted he had made a mistake.
Nancy Jr. - who was 10 when her father left - said: "I said, 'If you had it to do over again would you have left?' He said no."
However, the 75-year-old singer insists her mother never held a grudge against her ex-husband, who died in 1998.
She said: "She still loves and adores him, definitely."
And Nancy herself enjoyed a good relationship with Ava, and is also "very close" Frank's third wife, Mia Farrow, despite their volatile marriage.
Speaking of her dad's third reunion, she said: : "He said: 'I don't know that this will last but I'm going to try.' "
In 2013, Mia claimed Frank was actually the father of her son Ronan, not director Woody Allen, but Nancy insists the remarks were just a "silly joke".
She told The Times newspaper: "Mia's folly. She made a silly joke... Everybody knows whose son Ronan is... I think he looks like Mia. He's a great guy, by the way."