The tight Fast & Furious family showed a crack in the run up to the eighth film in the franchise, The Fate of the Furious, when Dwayne Johnson made a disparaging remark about some of his unnamed costars. "Some conduct themselves as stand-up men and true professionals, while others don't," he wrote. "The ones that don't are too chickens ... candy asses."

Vin Diesel in Fast 8 - Fate Of The FuriousVin Diesel in Fast 8 - Fate Of The Furious

While Johnson has since qualified those remarks, his costar Vin Diesel has stressed that they are a family who speak honestly to each other. "I think some things may be blown out of proportion," Diesel says. "I don't think that was his intention. In my house, he's Uncle Dwayne. He only has one big brother in this film world and that's me."

Diesel says that brotherhood is the main theme of the franchise. "The best part of Fast & Furious is not the big explosions, it's the heart," he notes. "When you think about the brotherhood of Dom and Brian, that's what carries through so many films. And no characters in history have carried on a love affair that has kept your attention for as long as Dom and Letty. It's to the point where a kiss from another woman [Charlize Theron] is the biggest action sequence in the trailer!"

Indeed, that kiss in the first Fate of the Furious trailer caused an internet storm, which surprised Diesel. "It's something as familiar and simple as a kiss," he laughs. "And that's why a little kiss can be so powerful! You really feel that Dom is in this conflicted place, and it makes for a very interesting story."

At 49 years old, Diesel is still amused by his status as an action hero. He originally planned to become a serious actor. "I feel like there are movies that have action in them and they might have comedy and romance moments as well," he says. "Does the action hero really exist? There isn't a school you go to to become an action hero. Maybe the term was invented by Hollywood, to focus on the physique of Arnold or something. Does the term truly exist or is it journalist shorthand?"

The Fate of the Furious is the first in a trilogy that will complete the franchise after 10 movies. Diesel has said that he already knows how it will all end, but that there's "tons of pressure" about how they'll get there.

Watch the trailer and featurettes for Fast 8: