Family comes first for Kevin Costner.
The Oscar-winning actor revealed to Fox News Digital that his 15-year-old son, Hayes, isn't the only Costner kid to show off his acting chops in "Horizon: An American Saga."
"They're all supportive of each other," Costner confessed of his seven children. "My oldest son was in a scene in chapter two, and, a small part again."
He joked, "I just try to find ways to trap them."
Costner shares sons Hayes,15, and Cayden, 17, and daughter Grace, 14, with ex-wife Christine Baumgartner. The former couple finalized their divorce in February after 18 years of marriage.
He also has three adult children – Annie, Lily and Joe – with ex-wife Cindy Silva, and son Liam, 26, with former partner Bridget Rooney.
KEVIN COSTNER ‘SELFISHLY’ GAVE ‘HORIZON’ ROLE TO 15-YEAR-OLD SON: ‘IT WAS A SMALLER PART’
While his older son makes his debut in the second part of "Horizon," his son Hayes was only 13 years old when he signed on to star in the first film of the post-Civil War drama which Costner began dreaming up more than 30 years ago.
Costner admitted working on set with Hayes, who was cast as Nathaniel Kittredge, was special in many ways.
"That he did it, that he was good in it, that he listened, that he was worried, that he cared … I'm just so happy that he has that now the rest of his life," Costner said. "I haven't pushed my children into this, and this might be his only dabble in it, but he's memorable. And for me to have him, I'll never forget it."
WATCH: KEVIN COSTNER TALKS ABOUT WORKING WITH HIS SON ON ‘HORIZON’
Hayes' role required two weeks of filming, which gave Costner a unique time to bond with his son.
"In a sense, it was a smaller part," Costner told "Today" about his son's role. "I selfishly wanted him with me for the week, two weeks, he was with me. And we would drive to the set every day and he would whisper. He didn't have a lot of experience, but he's really beautiful in the movie. It's a really complicated scene.
Costner released the first trailer for the four-part, post-Civil War drama in February, and showcased the Wild West frontier his name has become synonymous with for decades, dating back to his first directorial stint on "Dances with Wolves."
In addition to starring in the feature film, Costner also directed "Horizon," based on a script he co-wrote with John Baird. The ensemble cast includes Sienna Miller, Sam Worthington, Luke Wilson, Abbey Lee, Jena Malone and Giovanni Ribisi, to name a few.
The film came with a hefty price tag, though, and set Costner back many millions in out-of-pocket expenses, which came to light during his divorce proceedings.
Costner later clarified the massive sum. "I know they say I've got $20 million of my own money in this movie," he told GQ magazine. "It's not true. I've got now about $38 million in the film. That’s the truth. That’s the real number."
Costner's entire focus can remain on the future of "Horizon" now that "Yellowstone" is officially over for Mr. John Dutton. After months of speculation, Costner confirmed on social media last week that he wouldn't be returning to season five, part B of the Taylor Sheridan show.
When asked why he finally made the decision to leave the popular series, Costner's answer was simple. "Because there's just too many questions about it. So the time to step away was now," he told Fox News Digital.
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On Instagram last week, Costner said, "Hi, everyone. I just want to reach out and let you know that after this long year and a half of working on ‘Horizon,’ and doing all the things that's required, and thinking about ‘Yellowstone,' that beloved series that I love and I know you love, I just realized that I'm not going to be able to continue Season 5, or into the future."
WATCH: KEVIN COSTNER REVEALS HIS OLDEST SON IS IN ‘HORIZON’ 2
"It was something that really changed me. I loved it and I know you loved it. And I just wanted to let you know that I won't be returning. I love the relationship that we've been able to develop, and I'll see you at the movies."
Fox News Digital was in the courtroom where Costner hinted at a possible legal showdown over money he is owed from his time on "Yellowstone" while fighting over child support payments with ex-wife Christine Baumgartner. Before a judge ruled in favor of the actor in September over monthly child custody payments, Costner testified in depth about the drama surrounding "Yellowstone" season 5.
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"We did negotiate," he explained in the courtroom. "There were issues about creative. I tried to break the log jam. They walked away."
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Costner seemingly had issues with the timing of filming "Yellowstone" as he wanted to focus on "Horizon." At the time, the first movie in the four-part saga was in post production, a "critical" time for putting things together.
"Somewhere along the line they wanted to change things," he said of the "Yellowstone" filming process. "They wanted to do 5A and 5B… affected ‘Horizon.’ I was going to do my movie ‘Horizon’ and leave that show, do my movie, then do B. A show I was only doing once a year I was now doing twice."
Costner explained that he had been offered $24 million to do season five, six and seven of "Yellowstone," before scheduling broke down, and the show was canceled.
"I will probably go to court over it," Costner responded when asked by his ex-wife's lawyer if he had received a payout from the latest seasons of "Yellowstone."
Costner's western saga debuts in theaters on June 28. The second part of the epic will be released just 49 days later, on Aug. 16. Tickets are on sale now.
