As the writer-director behind cult hits like “Super” and “Slither” and the blockbuster “Guardians of the Galaxy,” James Gunn has worked with some of the biggest names in the business. But ask him who his favorite actor to work with is, and he doesn’t hesitate: it’s his brother, Sean Gunn.

He’s not just trying to keep family dinners peaceful. Sean is an accomplished teacher and actor, perhaps best known for his scene-stealing turn as Kirk on “The Gilmore Girls,” and has appeared in almost all of his older brother’s projects. “I’d rather have him as an actor than anybody else,” James notes. “We see things so similarly and having the same background, we have a shorthand of speaking. I can say something that would make sense to no one else, like, ‘Do it like Cousin Chuck would!’ ”

The new few weeks see two new collaborations between the duo. Opening this Friday, Sean stars in “The Belko Experiment” as one of 80 employees who are trapped in an office building and told to kill one another for survival; the film was scripted and produced by James and directed by Greg McLean. And in May, Sean will reprise his roles as “Guardians of the Galaxy Vol. 2” as Kraglin, one of the villainous Ravagers, as well as having performed the motion reference acting for Rocket Raccoon (voiced by Bradley Cooper.)

The two share a common sensibility; among other things, they agree that if they were put in a “Belko”-like situation, they wouldn’t kill anyone. But there are differences: James has little interest in sports, while Sean is a fan. Sean is a vegetarian, James is not. Perhaps most importantly: while Sean likes “The Bachelor,” he isn’t quite the fanatic James is. (During this interview, he correctly guessed the season’s eventual “winner,” Vanessa.)

Not only do the two say working together has never posed a problem, Sean says, “It’s actually easier to work for James than anyone else. We’ve been working together in some capacity since we were kids.”

The Gunns were raised in St. Louis, Missouri and though their parents had no connections to the entertainment industry, five of the six siblings have forged successful careers in show business. Brian and Matt Gunn are both writers, while Patrick Gunn is film executive and producer. Their sister, Beth, followed in their father’s footsteps and became an attorney. (And not an entertainment lawyer—she is what James jokingly calls a “real, helping-people lawyer.”)

Asked how they all ended up in entertainment, and James posits, “Other kids were really focused on being competitive in sports and academics, and all we ever cared about was making each other laugh around the table.” Agrees Sean, “That’s true, and I think imagination was encouraged in our house.” Even before he was a teenager, James was shooting zombie movies on an 8mm camera, starring his brothers.

James states that it probably helped that their family was “pretty dysfunctional.” He adds, “You know how people have gallows humor when they work in hospitals or police stations? We were in a family where crazy shit was happening and you deal with it through humor.”

The family generally hasn’t overlapped much with work, with the exception of James and Sean. “Our jobs just fit together without overlap,” Sean notes. Agrees James, “Matt and Brian are both writers. Patrick lives in New York. Sean is primarily an actor and I’m primarily a director, so we work well together.”

Their careers have charted similar paths, as well. One of James’ early breaks was scripting the 1996 cult hit “Tromeo and Juliet” for the low-budget studio Troma, a project that marked Sean’s feature film debut. In 2000, just as Sean’s TV career was taking off with “Gilmore Girls,” James’ had written and produced “The Specials.” A couple years later, he scripted his first big studio film, the live action adaptation of “Scooby-Doo.”

But James adds that while they’ve shared many highs, they’ve also experienced the lows at the same time. “Previous to ‘Guardians,’ I probably had my biggest downs,” James says, with Sean agreeing around 2010 he hit a lull.

“I was on ‘Gilmore Girls’ for seven years and had a couple decent years after that,” notes Sean. “Then two years of almost nothing. I had jobs here and there, but I got very, very scared. I was doing a little teaching and riding it out, but ‘Guardians’ came around and not only saved him in a big way, but saved me too.”

James says it’s no exaggeration to say that “Guardians” saved him. “I was at a point where I wasn’t sure I wanted to direct movies anymore,” he recalls. “I called my agent and manager and said, ‘Listen, I want to be relevant. There is no such thing as the type of movie I make anymore. There’s no such thing as middle of the road action adventure movies. The truly relevant films now are Marvel movies and spectacle films and no one’s going to give me that. So I’m going to quit directing movies and focus on TV and videogames.’ And I did that.”

Two weeks later, he got the call from Marvel to discuss “Guardians,” but says he didn’t take it too seriously. “I’d had these meetings before, I felt I was a name they crossed off their list,” he says. “I was actually complaining about it the day of the meeting, about how I had to drive all the way down to Manhattan Beach.”

James cast Sean in the first “Guardians” as the sidekick to Yondu, the leader of the Ravagers, played by Michael Rooker – who James has frequently cast since he directed him in “Slither.” But he also asked Sean to play Rocket on set. “I don’t shoot scenes in a vacuum,” James explains. “I didn’t’ want some AD off screen reading the lines in a monotone. We needed somebody to really interact with the actors. So I hired him as an actor to have someone to bounce off of.”

Sean ended up being so integral, he’s used even more in the second film. “In the first one, we would do a scene a couple times with Sean in and then move him out and do other takes. In the second one, we would use him until we got the scene just the way we wanted,” James notes. “In the first, if he wasn’t speaking, we didn’t shoot him at all. But in the new one, even when he’s not speaking, Sean is still acting as Rocket during the action shots.”

James adds that Sean is also vital to have on set to give him an added perspective. “People are learning that Sean is a huge part behind Rocket but what they don’t know is he’s also a big part of helping by coming up and whispering to me that Chris Pratt is fucking up a scene. Which happens every day,” James jokes. “But no, honestly, he seems things from the inside while I’m looking at them from the outside, which is amazing. I rely on all my actors to do that, but he’s a particularly great source.”

Sean is so trusted that when James handed him the script to “The Belko Experiment,” he asked him which role he wanted to play. James had written the script in 2007, after “I literally dreamed the trailer in my sleep; the trailer you see for the film is the trailer I dreamed 10 years ago.”

Though Sean briefly considered the role of Keith, played by Josh Brener in the film, he was ultimately drawn to Marty, a worker in the building’s kitchen, who is prone to paranoid conspiracy theories. “Marty is a little different from the roles I’ve been doing, but still something I could bring something to,” says Sean. He laughs when recalling how co-star John C. McGinley asked him what role he was playing when they got to set. “I told him I was Marty and he said, ‘Aw, best role in the movie!’” before adding, “On the page. On the page!’”

While not revealing Marty’s fate in the film, this isn’t the first time James has put his brother in harm’s way—he’s killed Sean off in previous films like “Tromeo” and “Super.” But James warns not to read too much into it. “A lot of people die in my movies,” he notes. “So if you’re in a few of my movies, you have a good chance of dying!”