John C. Reilly and Joaquin Phoenix play sibling outlaws in Gold Rush-era America.

A veteran of wacky double-acts, most notably with Will Ferrell in Step Brothers, Talladega Nights and recent Sherlock spoof, Holmes & Watson, John C. Reilly notably pairs with Steve Coogan for Laurel and Hardy drama, Stan & Ollie, although he reckons The Sisters Brothers might be his most bizarre duo ever, partnering with Joaquin Phoenix as the titular brothers.

“What’s so interesting about these characters is that even though they look like filthy brutes that are murderers for a living, they’re actually well-educated and have these somewhat intellectual conversations with each other,” Reilly tells STACK when we catch up with him at the recent Toronto International Film Festival.

“The brothers use that thing of judging a book by its cover to their advantage to always have the jump on people who assume they are less intelligent than they are – kinda like me and Joaquin,” he quips.

“These guys have spent their entire lives together and since they left home it’s just been the two of them so, since we had a lot of catching up to do, Joaquin and I spent as much time together as possible.”

Filmed on location in Spain, the notorious sibling outlaws – hitmen hired by a mobster known as The Commodore – head out across Gold Rush-era America on a mission to kill one Hermann Kermit Warm, portrayed by Riz Ahmed.

Based on Patrick deWitt’s 2011 eccentric neo-western novel, The Sisters Brothers is veteran French director Jacques Audiard’s first English-language film.

“For me it’s more like a fairy tale than a western,”

says the director, who signed on after Reilly’s wife Alison Dickey discovered the book and brought it to Audiard.

Representing Reilly’s first producing credit, he says, “I am technically a producer but it was my wife’s idea in the first place and she suggested Jacques. The book is a very compelling piece of work, a great piece of Canadian literature.”

“It felt really unique and different,” adds Joaquin Phoenix, one half of the Sisters Brothers, “and these two brothers have really vibrant personalities”.

If The Sisters Brothers is a violent and hilarious romp, then Reilly is one of the gentlest men you could meet – a long time devotee of Transcendental Meditation, off-screen priding himself on his snappy attire.

The son of an industrial linen supply company owner, he grew up in working class Chicago with five siblings, learning early on how to share the spotlight.

“Playing a sibling was not much of a stretch for me,” says Reilly, 53, who never set out to be a leading man, along the way becoming one of the most in-demand actors in Hollywood and discovering a new young audience as the voice of animated arcade game character, Wreck-it Ralph, reprising his role in recent sequel Ralph Breaks the Internet.

He remains amazed at his career trajectory. “Growing up in Chicago, I didn’t know anyone in show business when I was a kid and never dreamed that’s what I would do for a living,” says the actor who earned an Oscar nod for his role in musical Chicago, also featuring in The Hours, Boogie Nights, Gangs of New York and Kong: Skull Island.

The Sisters Brothers also serves as a reunion for Nightcrawler co-stars Ahmed and Jake Gyllenhaal.

“Jake and I were joking that it was a kind of sequel for us but instead of being in the car, we’re on horseback,” says Ahmed. “Its interesting working with the same actor again because you already have a shorthand and also to see how our dynamic was changed from Nightcrawler in terms of who is in charge.”

Admittedly Ahmed never envisioned starring in a western. “I just loved my character, Hermann, who just wants to make the world a better place. He’s such an optimist whereas I can sometimes be a cynic. It’s the British perspective to look at everything a bit skeptically.”

The Sisters Brothers is in cinemas on March 6.