NRL star Bradman Best is set to swap the footy field for the film set after landing a role in the upcoming biopic on Australian boxing legend Jeff Fenech - a project made even more personal by his deep ties to the fighter's family.

The Newcastle Knights centre will make his acting debut in FENECH – The Jeff Fenech Story, a film charting Fenech's rise from the tough streets of Marrickville to world champion status.

Best, who is engaged to Fenech's daughter Kayla, has been cast as former world champion Jeff Harding and will appear as a sparring partner in the film.

The casting is as much about family as it is about football.

Best and Kayla Fenech went public with their engagement earlier this year after a romantic proposal at the picturesque Krinklewood Estate in the NSW Hunter Valley. 

The couple, who have been together for several years, already share a young daughter, Kaliyah, with the toddler present during the proposal.

Their relationship has firmly embedded Best within one of Australia's most iconic fighting families, making his involvement in the film a natural fit.

Fenech himself admitted the idea hadn't initially crossed his mind, until it was suggested.

'They're looking into whether he could be added to the cast,' he said.

It didn't take long for that to change.

'Bradman's in the movie thanks to you!' Fenech later revealed.

'I asked them this afternoon and they thought it was a great idea.

'He's going to be a sparring partner. He'll be Jeff Harding.

'He thought we were just joking at first, but he's wrapt. He can't wait.'

Best's selection is not just based on family connections. The 23-year-old has a genuine boxing pedigree, having trained and fought in his younger years on the Central Coast.

Fenech has also seen that ability up close during training sessions.

'The way he hits, I always tell him, he could fight and beat most of these guys boxing today,' he said.

Directed by award-winning filmmaker Matt Norman, the film is aiming to deliver a raw and uncompromising portrayal of Fenech's life, focusing on the grit, sacrifice and resilience that defined his career.

Producers have placed a strong emphasis on realism, using real fighters in key roles and avoiding overly choreographed, Hollywood-style fight scenes.

The cast blends actors and sporting figures, with Daniel Amalm playing Fenech, Gary Sweet as legendary trainer Johnny Lewis, and Tim Tszyu cast as his father Kostya Tszyu. 

Broadcaster Ben Damon will also appear as a commentator, while Fenech's daughters will play themselves.