In his first public comment about his father's illness, the 46-year-old actor said it's "a rough thing", reported Ace Showbiz.
"It's one of those things where if somebody had said 10 years ago, when my dad and I were joking around, having a putting match, that this is the position your dad's going to be in, where he basically needs 24-hour care, you'd think, 'Gosh, I won't be able to handle that.
"That's just not possible'. You just have to do your best to deal with it. You've got no choice but to accept it. And then, you sort of still look for the things to be grateful for," he said.
He was the one who propelled Jim Lehrer to become the host of "The News Hour with Jim Lehrer".