A 22-year-old former addict wrote a script about life in rehab - now his famous dad Rob Reiner turned it into a movie

For the last 30 years Rob Reiner has been known best for directing memorable movies like "Stand by Me," "The Princess Bride," "When Harry Met Sally," and "A Few Good Men." The titles have brought happiness and entertainment to millions of people.

But the Reiner household has been anything but happy, as the legendary actor/filmmaker's son, Nick, 22, has been battling drug abuse since his late teens.

Most families would want to keep that part of their lives as hidden from public view as possible. But Reiner admits that at the darkest moments of his son's addiction to hard drugs he thought of making a movie. However, it was too painful to put pen to page and begin a script.

Interestingly enough, his son came to the same realization as a means to rehabilitate.

While at a rehab center in Los Angeles four years ago, Nick befriended fellow addict Matt Elisofon. The two began writing about their challenges with addiction and the people they met at rehab. Eventually they came up with a script for the movie "Being Charlie," which they asked Rob to direct.

The film had its world premiere at the Toronto International Film Festival to a sold out crowd earlier this week.

It's a mixture of drama and comedy that focuses on an 18-year-old named Charlie (played Nick Robinson of "Jurassic World" fame) as he struggles with addiction from heroin and cocaine. As Charlie jumps in and out of rehab, the aggravation of his actor-turned-politician father (Cary Elwes) grows as he doesn't know how to help his son.

"It was a real corrective emotional experience," Nick Reiner told Business Insider following the TIFF screening about making the movie.

It took "Being Charlie" four years to get to the screen (in that time Nick has been sober). Evolving from a half-hour comedy, then an hour dramedy that was rejected by the TV networks, to finally a feature film.

According to Rob Reiner, what the project lacked in its early development was telling both the father and son's sides.

"It needed what he has been through but also what we had been through," Rob told Business Insider, referring to himself and his wife, Michele, who was sitting beside him.

Nick and Elisofon were by Reiner's side throughout filming. According to Rob, the script was tweaked daily to make the scenes more true-to-life.

"I relied on him," Rob said of his son. "He's the heart and soul of the film."

One of the biggest adjustments came while shooting the film's ending, where Charlie and his father finally have a heart-to-heart.

Rob and Nick couldn't find the right tone. After constant rewrites, they finally felt they had something a few days before shooting the scene. It's a gripping moment where both the father and son open up to each other like they never have before.

The Reiners compare getting the ending right to the whole experience making the film.

"We were healing as we were going along," Nick said. "And it all doesn't happen over night, certain things we hadn't dealt with for a while but we were able to through this movie. It didn't fix everything, but it really tapped into -"

Nick paused to find the words, then his father, sitting across from Nick, finished for him.

"It forced me to really have to understand what he had been going through for a long time," Rob said.

"Being Charlie" is currently seeking distribution.