Kevin Costner is happy to give his son a leg up—just this once. 

Indeed, the Yellowstone star recently shared why he decided to cast his 15-year-old son Hayes in his new film Horizon: An American Saga. 

"He's a beautiful boy," Kevin—who shares Hayes as well as kids Cayden, 17, and Grace, 14 with ex wife Christine Baumgartner—explained on the June 17 episode of Today. "And he's quiet."

And the Field of Dreams actor noted that his choice to cast his son in the first installment of what will be a four-part franchise—a Western story that has been over 30 years in the making for the Oscar winner—goes against the rules he's set for himself. 

"I have not shoved my children into the business," the 69-year-old continued. "I realize there's so many young actors that would just kill to be in this movie and I don't want to take those parts away from them just ‘cause I can place my own children in. But in this instance, it was a smaller part. I selfishly wanted him with me for the two weeks he was with me."

Kevin—who directed and starred in the film—went on to note some of the memories he was able to make with his son on set. 

"We would drive to the set every day and he would whisper," he recalled. "He didn't have a lot of experience but he's really beautiful in the movie. It's a really complicated scene."

The upcoming film just debuted at Cannes Film Festival last month, receiving a seven-minute standing ovation. However, the part that left Kevin speechless was the fact that five of his seven children—which also include Annie, 40, Lily, 37, and Joe, 36, who he shares with ex Cindy Silva as well as Liam, 26, who he shares with ex Bridget Rooney—were present for it. 

"I wasn't expecting that," Kevin, who was joined by all of his kids except Joe and Liam at the recent premiere, explained. "I looked to my left and there were my five children all dressed up and looking at me. I really didn't know what to do. I just shut out the noise." 

The first installment of Horizon: An American Saga hits theaters June 28. 

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