Kevin Costner's son Hayes may not have even been born when his dad first started working on his epic Western saga, but he's had a huge impact on it now that it has finally come to fruition.

He was joined by three of his children: daughter Grace, 14, and sons Cayden, 17, and Hayes, 15, whom he shares with ex-wife Christine Baumgartner. Related: Kevin Costner's 7 Kids: All About His ...