In his bestselling book – “All in the Family: The Trumps and How We Got This Way" – Greenwich resident Fred Trump III paints an unflattering picture of his uncle, former President Donald Trump, but he says the real purpose of the memoir is to advocate for people with intellectual and developmental disabilities.

"I don't want this story to be Donald-centric," the 61-year-old said during a sit-down interview at his home.

Fred Trump's youngest son, William, 25, who lives in a Connecticut group home, has the genetic variant KCNQ2 and a seizure disorder. He requires lifelong care.

"William is wheelchair-bound. He needs assistance for everything he does, but I will tell you, there is something so meaningful inside of him," Trump said. "The number one issue that we're fighting for is caregiver training and caregiver funding, because there is a severe shortage of both. Whether you're a Republican or a Democrat, you either know somebody or you yourself are disabled.”

Trump is a registered Democrat who has publicly endorsed Vice President Kamala Harris over his uncle in the upcoming presidential election.

"Right now, Donald's character is getting in the way more than I ever thought it would possibly be," Trump said.

He recently started a nonprofit called William's Journey to promote care for people with intellectual and developmental disabilities.