Charlie Hunnam has joined the cast of 'A Million Little Pieces'.

The 'Sons of Anarchy' star famously turned down the role of Christian Grey in the 'Fifty Shades of Grey' movie, directed by Sam Taylor-Johnson, but the pair will now work together on the big screen adaptation of James Frey's bestselling book about battling addiction, according to The Hollywood Reporter.

Charlie will play the brother of the lead character, 23-year-old alcohol and drug abuser James, a role that has already been filled by Sam's husband Aaron Taylor-Johnson.

Billy Bob Thornton has also boarded the project as a mafia boss James meets in rehab, who becomes a great support in his recovery.

And 'Blade Runner 2049' actress Carla Juri has signed up to play the female lead, a crack and heroin addict who falls in love with James.

'A Million Little Pieces' tells the story of a 23-year-old alcoholic and drug abuser and deals with how he copes with rehabilitation in a 12 steps-orientated treatment centre.

Originally published as a memoir, it shot to the top of the bestseller list after being featured Oprah Winfrey's book club in 2005.

But the book was hit by controversy when The Smoking Gun published an investigation claiming the book was a fake, which saw it remarketed as a 'semi-fictional novel'.

Warner Bros. originally bought the rights to the book and set it up with producer Brad Pitt and his then-Plan B partners Jennifer Aniston and Brad Grey, but the project was later shelved.

Husband-and-wife team Sam, 50, and Aaron, 27, have brought it back into production.

The couple met when Sam directed Aaron in John Lennon biopic 'Nowhere Boy' in 2009.

In May last year, Sam talked about a secret project she is working on with her husband, and said: ''We are already parents that run our house, so when we together it's the best.''