Stephen Graham has said it was Paul Bettany's idea for the pair to play brothers in new film Blood.
The pair co-star as Joe and Chrissie Fairburn, fraternal detectives investigating the murder of a 12-year-old girl, in the British crime thriller.
Liverpool-born Boardwalk Empire actor Stephen, 39, said of the film: "It was a great thing to do with Nick Murphy, who's a great director. I worked with him on a production called Occupation a few years ago with James Nesbitt.
"I'm really good friends with Paul Bettany, and I think it was Paul's idea - he said 'Can me and Steve play Brothers?', and Nick said: 'Well, he's dead little and you're dead tall.'
"It was like, 'Yeah, not all brothers are identical, are they?'."
Stephen, known for his roles in Snatch, Public Enemies, This Is England and recently, Parade's End, said: "It's a great role and such a fantastic script. It's nice for me to not be the aggressor for once.
"We're playing police officers in a kind of corrupt society and a corrupt police force."
:: Parade's End is out now on DVD and Blu-ray.