The comic complications of sibling crises dominated Wednesday’s Los Angeles premiere of Radius’ “Adult Beginners” at the ArcLight.

“I’m the youngest of four, so the movie is very relatable to me,” noted Rose Byrne, who plays the older sister to Nick Kroll’s character.

In 2011, Kroll and Mark Duplass began developing the idea for the film, in which a semi-desperate man moves in with his sister after his business and personal life fall in disarray.

“I have 12 nieces and nephews, so the movie seemed like a good idea at the time,” Kroll said. “My character is messy, like a lot of people in real life.”

Kroll noted that a non-functioning pool heater forced him, Byrne and Bobby Cannavale to spend several days in chilly pool water for key scenes shot during the 2013-14 winter. “That was the toughest part because the water was so cold,” he mused.

Ross Katz, whose producing credits include “In the Bedroom,” “Lost in Translation” and “The Laramie Project,” allowed that he wasn’t the logical choice to direct the Jeff CoxLiz Flahive script — given the seriousness of the work comprising his background. “I had to convince Nick, Rose and Bobby — who were all attached at that point — that I’m a funny guy,” he recalled.

“Adult Beginners” premiered at Toronto, where Radius acquired it shortly after that screening. “It didn’t have a home when we showed it at the festival, which is kind of nerve-wracking, as opposed to tonight,” he added.

At the post-screening L.A. bash at Wood & Vine, Katz expressed gratitude that, after his own brother, Mark, had requested a premiere in San Francisco, Radius complied by planning an event on Saturday.

“We have very different lives, since he’s an attorney with kids, so they can never go out,” he explained. “So they’ve lined up a babysitter for Saturday.”

“Adult Beginners” will also have a New York premiere next week prior to its April 24 opening.


(Pictured: Actors Nick Kroll and Rose Byrne at the premiere of  “Adult Beginners” at ArcLight Hollywood)