Kevin Costner Discusses Son Hayes' Acting Debut in 'Horizon' and Final Season of 'Yellowstone' (Exclusive)

For Kevin Costner, watching his son, Hayes, grow up served as a constant reminder that had to get moving on his passion project, Horizon: An American Saga.

On Tuesday, the famed 69-year-old actor-director exclusively spoke to ET's Cassie DiLaura during the Warner Bros. Pictures presentation at CinemaCon 2024 in Las Vegas, Nevada, where he shared that he named his now-15-year-old son after the protagonist he portrays in his decades-in-the-making Western epic. Fast-forward to now, and Hayes will make his acting debut in the very film Costner first started working on in the late 1980s.

"I named him after the character I play in this. My character's name is Hayes Ellison," Costner told ET. "And I named Hayes that character. So I was watching him grow up and I was thinking, 'Man, I better get with it and make this movie.'"

Horizon has been more than three decades in the making. It has taken so long to develop largely because Costner was highly sought after in Hollywood. But he never lost sight of his goal to bring Horizon to the big screen, and what ensued was a path of hope fueled by his relentless determination. Costner said it took him and co-writer Jon Baird six years to write the scripts to his four-film saga, a project that was originally under the Disney banner before it ultimately wound up at Warner Bros. And as the months turned into years and the years turned into decades, Costner's sheer doggedness and pursuit remained fiery as ever.

The cherry on top all these years later? Costner's son joining him on this project.

"I captured him and I brought him on, and he's very good in this small part that he's done," Costner gushed. "If you see it, I think he has an impact on the movie."

And for the record, Hayes -- whom Costner shares with ex Christine Baumgartner, along with son Cayden, 16 and daughter, Grace, 13 -- did not have to audition for the role.

"No, listen. I don't give great parts away. I understand that there's young actors out [there] that would kill for these parts," Costner explained. "And so mine have to respect the profession. But in certain instances, this was something I thought he could handle. I wanted him close and so I did it. So we're locked together in a film forever. Actually, I'm not in any scenes with him, but I directed him when he was little and now he's big."

Horizon: An American Saga is set in the pre-and-post-American Civil War period, depicting the expansion of the American West. All in all, Costner's ambitious project will total four films. The official description for the film says Horizon "explores the lure of the Old West and how it was won -- and lost -- through the blood, sweat and tears of many. Spanning the four years of the Civil War, from 1861 to 1865, Costner's ambitious cinematic adventure will take audiences on an emotional journey across a country at war with itself, experienced through the lens of families, friends and foes all attempting to discover what it truly means to be the United States of America."

Costner acted in, directed, and produced the two-part theatrical event. In an unprecedented move, Chapter One will hit theaters June 28, followed by Chapter Two on Aug. 16. The film stars Danny Huston, Luke Wilson, Sienna Miller, Sam Worthington, Jena Malone, Abbey Lee, Michael Rooker, Isabelle Fuhrman, Jeff Fahey, Will Patton, Tatanka Means, Owen Crow Shoe, Ella Hunt and Jamie Campbell Bower.

Horizon became such an ambitious project, Costner told Deadline in May 2023 that he mortgaged "10 acres on the water in Santa Barbara" in an effort to get his passion project off the ground. So is Costner nervous ahead of Chapter One's release?

"No," Costner told ET. "I feel really good about what this movie, what it does to me. It was the kind of movie that I hoped someone would make for me. That's what I like to see."

And speaking of cowboys, Costner also opened up to ET about Yellowstone's upcoming fifth and final season. The show was originally scheduled to return in late 2023, but there was a lot of tension between Costner and co-creator Taylor Sheridan, not to mention the Hollywood strike. But now part two of season 5 is expected to drop in November, and it's Costner's hope to maybe one day get back in the fold.

"I'd like to be able to do it but we haven't been able to," Costner said. "...I thought I was going to make seven [seasons] but right now we're at five. So how it works out -- I hope it does -- but they've got a lot of different shows going on. Maybe it will. Maybe this will circle back to me. If it does and I feel really comfortable with [it], I'd love to do it."

And, yes, Costner says he's thought about how John Dutton's story wraps up in Yellowstone.

"Well, you know, he needs to be proactive in what happens and I've kind of had my own fantasy how it might be," Costner said, "but that's Taylor's thing. I said as much to him a while back. I had thoughts how it could happen, but we just have to see."

‘Yellowstone’ Final Season: Kevin Costner's Involvement and Where Sequel Series Stands (Report)

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‘Yellowstone’ Final Season: Kevin Costner's Involvement and Where Sequel Series Stands (Report)

And whether it's Costner or anyone else for that matter, it seems like almost everybody's out of the loop when it comes to what's going to happen in the last and final season of Yellowstone. ET caught up with country superstar Lainey Wilson at the 2024 CMT Music Awards over the weekend in Austin, Texas, where she admitted she doesn't have many details about the upcoming installment. But she did say she'd be surprised if her lovable character, Abby, doesn't make an appearance.

"I'll be honest with you. I'd be shocked," Wilson told ET. "And I think how [series creator] Taylor Sheridan writes his stories, and he just has a beautiful way of bringing things back and letting things go -- I'll be shocked. So, we'll see what happens."

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