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

Kevin Costner's son is following in his father's footsteps.

The actor's son Hayes will appear in Costner's upcoming four-part Western epic Horizon, he tells PEOPLE exclusively in this week's issue.

"He's very good," says Costner, who's directing the project. "Hayes plays the namesake character that I actually play in the movie. He's 13 years old and the screenplay's been around longer than that."

While acting certainly runs in the family, the Oscar winner — who is also dad to son Cayden, 15, and daughter Grace, 12, with wife Christine Baumgartner (Costner is also dad to daughters Annie and Lily, and sons Joe and Liam from previous relationships) — jokes that casting his son also gave him an excuse to spend more time with him.

"I kind of did it on purpose, so he could be hanging out with me," he says. "And the same thing for Cayden, same thing for Grace. I'm like any other parent, I'm trying to figure out, like, 'This is really neat. You should come be with me.' "

Costner says the upcoming film (part one is complete and production will start on the second in the spring) is one that's especially important to the actor.

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"Horizon is incredibly meaningful to me. It's really been the hardest thing I've ever done, but it's exactly what I want to do," he says. "I wrapped this first one, and it took everything I had, but I'm holding on to the rope and not letting go. In my career I've tried to choose not based on what was popular. I made the films I wanted to make."

For Costner, who won a pair of Oscars for 1990's Dances with Wolves, the actor has long been drawn to stories about the Wild West.

"A lot of times we measure ourselves against other generations," he says. "I think about what was at stake. How did people survive? There's a rawness and an unpredictability about it. I'm haunted by that."

In his latest project, Costner explores the history and wildlife of Yellowstone National Park in honor of its 150th anniversary in a new docuseries Yellowstone One-Fifty, steaming now on Fox Nation.

Sharing the history of Yellowstone was important to the actor after he learned how the park came to be back in 1872.

"We take a lot for granted, but because people risked a lot, we all have much richer lives," he says. "Contributing my time toward the story seeing more light of day is just a tiny thing."