John Travolta and Kelly Preston's new Gotti biopic has won the seal of approval from the infamous mob boss' family and friends following a private screening on Sunday night (10Jun18).

The Grease star portrays the late leader of the powerful Gambino crime family in New York City in the new movie, with John's real-life wife Kelly playing Gotti's widow, Victoria.

The actress got the opportunity to really get to know Victoria as the film was being developed, and forming a friendship with her movie subject really helped Kelly understand her character's thoughts and feelings in different scenarios.

"First of all, it's daunting to play someone who is alive... her husband is so iconic," Kelly told breakfast show Good Morning America on Monday (11Jun18). "But she's amazing; she is smart, funny, kind, she was open and warm. She cooked us lunch, a beautiful Italian lunch, kids were coming in and out (of her house).

"We became friends via email as well, so I could ask her anything I wanted about how she was feeling, what she would say."

Their close connection allowed Kelly and John to tweak the dialogue in the script to ensure it was spot on.

"This movie is so real, there's not one word that's in it that wasn't said; it's a real behind-the-scenes look at this family," Preston explained.

The new biopic, which spans several decades of Gotti's rags-to-riches life, premiered at the Cannes Film Festival in France last month (May18), and on Sunday - the 16th anniversary of the mobster's death - the acting couple was able to receive personal feedback from the extended Gotti family - and Kelly was flattered by the "amazing" response.

"We had a screening with the family yesterday," she shared. "It was the entire family, all of their friends, everybody who knew John Gotti, who (still) knows the family, and it was amazing, the reception and the reaction was absolutely (amazing).

"It was the greatest gift I could ever be given as an actor of how they felt about the film."

Gotti, directed by Kevin Connolly, opens on Friday (15Jun18).

John Gotti lost his battle with cancer in 2002, while serving a life sentence for five murders and illegal gambling charges, among others.