"Anybody who's divorced will tell you that the transition at the end of the summer, which, as a father, is the one time of year where you get to spend a lot of time with your kid, is very painful," he told Entertainment Weekly.
"You get confronted with the facts of your divorce. It's always a very painful moment for me. So that made it into the beginning of 'Before Midnight'," he added.
He is now married to Ryan Shawhughes and the couple has two children.