Los Angeles, Aug. 10 -- Casey Affleck had been working on a script about a parent and child for years. He'd written scenes about a bedtime story and an argument about taking a trip into town and things seemed to be going well. As the father of two boys, Affleck had defaulted to writing the child as a son. But then, deep into the process, his boys came back with a request: They didn't want it to be about them.

"They were pretty adamant that they did not want it to be a father-son story," Affleck said. "I had already put in a lot of work and I was like, don't do it ... "

But, despite the heartburn of having to rework the story again, he caved and made the child a girl, and it ultimately helped the story. He'd been looking for stakes in th...