Ryan Phillippe reveals how son Deacon ended up on his new show — playing his brother

Like father, like son. 

Ryan Phillippe’s new role on Prime Video’s “Motorheads” turned into a family affair — as his son, Deacon Phillippe, 21, plays his brother onscreen.

“It was the showrunner’s idea, John A. Norris,” Ryan, 50, exclusively told The Post. 

“He came up to me and said, ‘We’re thinking about offering the role of Christian in flashbacks to your son.’ I was like, ‘wow.’ And internally I’m like, ‘please!’”

The “Cruel Intentions” star explained, “I wanted it, but I wanted to play it very cool and let them work it out, separate of me. I said, ‘Well, then offer it to him, and see what he thinks.’ And then [Deacon] said he wanted to – what a joy.”

Ryan shares Deacon with his ex-wife, Reese Witherspoon, 49, whom he was married to from 1999 to 2008. They also share daughter Ava, 25. (Ryan has a third child, daughter Kai, 13, with his ex, “Pitch Perfect” actress Alexis Knapp).

This is Deacon’s second role, after appearing in the Netflix series “Never Have I Ever.” 

“Motorheads” (premiering May 20 on Prime Video) follows high schoolers Zac (Michael Cimino) and Caitlyn (Melissa Collazo), who move with their mom (Nathalie Kelley) back to her Rust Belt hometown, where there’s a thriving street race scene. They’re close with their uncle, Logan (Phillippe), a former NASCAR mechanic who now struggles to keep an auto body shop afloat. 

Logan’s younger brother and the teens’ father, Christian, was a legend in the street race scene, but vanished under mysterious circumstances 17 years ago. 

“We didn’t have scenes together, but he was playing my brother. And so, we sat in a room with John the showrunner…and talked about what our childhood would have been like growing up – which is such a unique thing to have with your son,” Ryan told The Post. 

He added: “I was there on set for him for a lot of his initial work days, just in case.”

“The Lincoln Lawyer” actor explained that since acting is new to his son, he was on set “just to kind of show him the ropes, and let him know how things typically go, or if he had any questions.”

“I was there for his first night shoot, watching him be bleary-eyed at three in the morning,” he recalled. “So, it did feel like a shared experience, even though we weren’t onscreen together.” 

The show was filmed in Ontario, Canada, which meant that Ryan had to relocate for five months. He didn’t get to see his family as much, so it was “gratifying for me to have [Deacon] come up off and on throughout the production,” he explained. “And just to get to spend that time together.” 

Deacon is currently enrolled at New York University.

“Things change once your kids get older and move out,” the “I Know What You Did Last Summer” star said. “And so, the fact that we would get to live together for a few days here and there during the making of the show was really awesome.” 

When asked what advice he gave his son, Ryan said, “He’s a very sharp kid. I get advice from him often!”

“He grew up around [the TV and film industry] too, with his mother and with me. It’s not like he’s walking into a foreign situation,” he explained. “Our kids spend time on sets. And, I’m enjoying seeing him grow into it, and own it.” 

Nevertheless, he did give Deacon some space on one particular day of shooting.

“He did have to do a scene with a girl – like, a kissing scene. I’m like, ‘I won’t be there for that!’” he quipped.

Ava Phillippe has also done some acting roles in “Doctor Odyssey” and “Ransom Canyon.”

As for whether she’d join Ryan and Deacon on “Motorheads,” her famous dad told the Post: “That would be up to the guys that are calling the shots – but, you never know!”