How did Frankie Valli's daughter die?

Frankie Valli's daughter Francine died from an accidental drug overdose in 1980. He also had a stepdaughter named Celia who had died six months prior in an accidental fall from a fire escape.

Francine was 20 at the time of her death. She had been working to enter the music industry as a singer. She is buried at Glendale Cemetery in New Jersey.

The death of Francine was depicted in the film and musical "Jersey Boys," but the death of Celia is omitted. Writer Rick Elice explained in an interview that this was done intentionally because it would have seemed too unbelievable.