Knight, 39, died Tuesday outside Atlanta, said Madison, a photographer and founder/creative director of Obvious magazine.
No cause of death was released.
"We are still processing the untimely death of our son, brother, friend, and uncle. Mychael meant everything to us and we loved him dearly. He was generous and so full of life. This is how we choose to remember his legacy."
Lifetime, the network that airs "Project Runway," also released a statement to CNN.
"We are saddened to hear about the passing of a member of the 'Project Runway' family, designer Mychael Knight," the statement said. "It's a loss of a great talent and we wish his family peace and solace during this difficult time."
Born in Nuremberg, Germany, Knight grew up in Montgomery, Alabama, and graduated from high school in Washingtonville, New York.
After attending Georgia Southern University in Statesboro, where he earned a degree in apparel design and merchandising, Knight broke into the fashion industry while working as an intern at Wilbourn Exclusives in Atlanta in 2001.
An established fashion stylist, he was initially rejected when he auditioned for the second season of "Project Runway," which aired on Bravo at the time.
He eventually made it on to season three, where he won the fan favorite award and placed fourth in the overall competition.
Knight debuted his self-named fashion line on BET's "Rip the Runway" in 2007.
Hailed for his sexy and flattering women's wear, he was also featured on "Project Runway: All-Star Challenge" in 2009 and was a contestant on the third season of "Project Runway All Stars" in 2013.
The designer inspired tributes on social media from friends, fans, members of the fashion community and Bravo's Andy Cohen, who reminisced about Knight's appearance on the reality show "The Real Housewives of Atlanta."
Madison remembered his friend of almost a decade as a "true Southern gentleman."
"No matter what situation or industry event we attended, he always remained himself," Madison wrote in a tribute to Knight posted on the Obvious site.
"I admired that about him."
During a showing of his spring 2012 collection at New York Fashion Week, Knight talked to The YBF
about fulfilling his dreams in the fashion industry.
"You have to work for it," he said. "This whole process was hard as hell. I cried a lot this year. You can't give up."