Rob Reiner tried to help his badly “spoiled” son Nick by directing a 2015 film the nepo baby wrote with a rehab pal — but it apparently did tragically little to improve their fractured bond.

The father-son duo teamed up to work on Nick Reiner’s semi-autobiographical movie “Being Charlie,” about an 18-year-old addict being pushed into rehab by his dad, a former movie star running for Congress

The legendary director dad pulled out all the stops for the film — lining up “Princess Bride” star Cary Elwes to play himself and rising phenom Nick Robinson, who also appeared in “Jurassic World” in 2015, to play Nick.

Common, who was just off a role in Oscar-nominated “Selma,” was also among the cast. He also lined up award-winning cinematographer Barry Markowitz, who did “Sling Blade” and later Reiner’s documentary on Albert Brooks.

But the film was a flop, and critics panned it for the “surfeit of clichés” in Nick’s script.

It barely grossed $30,000, according to The Numbers web site.

The father and son didn’t exactly get the working relationship they may have wanted, either, a set worker told Page Six on Monday.

The pair had at least one vicious argument in front of thecast and crew during filming, said stunt performer Erik Audé.   

“They’re just going off on each other,” the witness said. “You could tell [Nick] was spoiled and Rob was just sick of his s–t.

“I just assumed, whether this is correct or not, this kid must be pushing all his buttons,” Audé said. “Rob can’t do anything right.

“[Nick’s] s a nepo-baby, a spoiled kid to the tee.”

Rob admitted during a Q&A shortly after the film’s release that, “At times, it was really rough’’ navigating how to depict the relationship at the center of the film.

Nick, 32, always felt he was living in the shadows of his dad, 78, and equally famous late comedic grandad, Carl Reiner, a source told Page Six on Monday.

Nick is now charged with murder after he allegedly fatally slit the throats of father Rob and his mom Michele over the weekend following a blow-out fight.

“I think he really resented his dad — or maybe hated himself — for not being as talented, prolific or beloved as his dad or grandad.” the source said of Nick.

Rob dished about his failed son’s many drug-addiction-treatment stints during an interview in September 2015, the same month the pair’s flick debuted.

But the beloved seemingly guilt-ridden Hollywood legend appeared to take the fall for at least some of his son’s issues.

“When Nick would tell us that it wasn’t working for him, we wouldn’t listen,’’ Rob told the Los Angeles Times of Nick’s rehab attempts.

“We were desperate, and because the people had diplomas on their wall, we listened to them when we should have been listening to our son.

“We were so influenced by these people. They would tell us he’s a liar, that he was trying to manipulate us. And we believed them,” Rob said.

Nick repaid his dad in an interview after the flick came out by noting the pair didn’t “bond’’ when the son was younger, but he did claim that filming his movie made them closer.

“It really clicked for me because we didn’t bond a lot as a kid,” Nick said in an interview with BUILD Series in May 2016.

“He really liked baseball, I liked basketball, and he could watch that with my brother — baseball. But I just, when I saw him [working on the film], it was something that I’m interested in, I was like, ‘Wow, he really knows a lot,’ and it made me feel closer to him.”

Rob responded, “It’s interesting that Nick would talk about it in that way because we did share that experience.

“You know, even though I’ve had a lot of experience making movies, and I said this to him many, many times, that he was the heart and soul of the film.”

“So, when it came to making the film deeper and better, I would have to really defer to him,” Rob said. “I relied on him for giving it the honesty and the truth that it has.”

Rob, 78, and his wife Michele, 70, were found dead at their Brentwood, Los Angeles home Sunday.