Kevin Costner Says He Named Son Hayes, Who Makes Acting Debut in “Horizon”, After His Character in the Movie

"I was watching him grow up and I was thinking, 'Man, I better get with it and make this movie,' " Costner told 'Entertainment Tonight' of the 15-year-old

The arrival of Horizon: American Saga is better late than never for Kevin Costner.

Ahead of the release of his two-part Western film, the actor revealed in a conversation with Entertainment Tonight that not only has the project been in the works for years, but his character, Hayes, was the inspiration for his now-15-year-old son's name — and fittingly, the real-life Hayes makes his acting debut in Horizon alongside his dad.

"I named him after the character I play in this. My character's named Hayes Ellison," Costner, 69, told ET on Tuesday, April 9, at CinemaCon in Las Vegas. "And I named Hayes [after] that character."

"So I was watching him grow up and I was thinking, 'Man, I better get with it and make this movie!' " the two-time Academy Award winner added. "So I captured him and I brought him on, and he's very good in this small part that he's done. If you see it, I think he has an impact on the movie."

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In the trailer, which dropped Feb. 26, Hayes stars in a tense scene that shows him helping a woman (played by Sienna Miller) and young girl, who are presumably his mother and sister, into a shelter through an opening in the floor as their home is attacked.

"It's all right — I'm gonna be with Dad," he tells Miller's horrified character, before closing the door on their hiding spot.

Costner — who directed, co-wrote and stars in Horizon — told ET on Tuesday that Hayes didn't have to audition for his role, explaining, "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."

But that doesn't mean the father of seven normally "give(s) great parts away."

"I understand that there's young actors out [there] that would kill for these parts," Costner said. "And so mine have to respect the profession. But in certain instances, this was something I thought [Hayes] could handle."

Related: Kevin Costner Reveals 13-Year-Old Son Hayes Will Appear in His Epic Western 'Horizon' : 'He's Really Good'

Also on Tuesday, Costner appeared onstage for distributor Warner Bros.’ presentation of upcoming titles at CinemaCon to promote Horizon, which is set during the American Civil War.

“I think about the promise of America,” he said from the stage. “There was a promise out here that if you could go, if you were tough enough, if you were mean enough, if you were resourceful enough, if you were lucky enough, you could take what you wanted in America.”

In reference to Native Americans, Costner added, “That promise meant that we stepped on a whole group of people that had been here for thousands of years.”

Horizon includes that struggle as well, he said: “If you could come west, if you could survive it, you could make a home and at the expense of a lot of things. So to me, that's drama.”

Horizon: An American Saga Chapter 1 is in theaters June 28, followed by Chapter 2 on Aug. 16.

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