When Michael was diagnosed with Parkinson's in 1991, he and Tracy only had one child, a son named Sam. Since then, they've added three little girls to their family.
How does a dad explain Parkinson's to small children? Michael says he simplifies the disease by explaining that his brain works differently than other brains.
"I won't talk in terms of something wrong or something broken or some illness or sickness," he says. "I'll just say, 'My brain doesn't get the messages the way your brain sends the messages to your body.'"