The actor admits he initially threw writer/director Shana Feste's script away - because it was "too heavy" - and had to be persuaded to pick it up again by his movie partner.
He says, "This young woman had written this beautiful script, called The Greatest, and it's about the loss of a son and my son, Sean, I almost lost him a number of years ago in a terrible accident.
"You get that dreadful call at 4.30 in the morning and he got airlifted out and he survived, and this film is about the loss of a son and the family coming together again.
"When I read it I said, 'No, I don't wanna go there, it's too heavy,' and threw it under the bed and then my partner... said, 'Look, check it out again, You've gotta do this,' so I read it again and said, 'OK, let's go for it.'
"It's a beautiful film... It's a really tender, powerful film."