Michael J. Fox's Personal Battle

Tracy says having Michael as a father has helped their children be more empathetic. "They just have a natural understanding of what's comfortable for Michael and what's not," she says. "They're not scared about it, but they just understand."

At times, Tracy says the children describe Michael as "shaky Dad." "They would never say 'Parkinson's' or they wouldn't say 'sick,'" she says. "['Shaky' is] sort of more of a visual description to them."

"I am shaky Dad," Michael says.

Michael says living with a chronic disease has helped him realize that every little moment is special. "If I'm sitting watching TV or something, and my kids come and want to show me something or want to ask me something, I just made up my mind that there's nothing that I'm doing at any time that's more important than that," he says. "I don't know that I would think that way before this happened. … So as long as I can get there, I'll be there."