Fred Trump Ill of Greenwich -- President Donald Trump's nephew - spent Saturday getting the word out about National Rare Disease Day.

"It's critically important to build awareness and to advocate for all of the families whose loved ones have rare diseases," he said.

Trump's son, William, is severely disabled as the result of a rare genetic mutation.

"Families need communities, and the idea is to tell the stories of what's happening to their child right now, and there are amazing scientists out there and I've seen firsthand what miracles they can accomplish," he said.

Trump said his goal is to change how the American public views and treats people with disabilities, arguing against the notion "that they are less than".