Kelly was raised as a typical dairy farm boy, waking each day at 4.30am to help milk cows. But, as he grew, he found his passion for design and fashion.
He had an exchange year in Denmark in Year 12, which his parents credit as the start of his design career.
"That's where it started," his mum said. "The experience gave him the taste to design in a big place."
Kelly's sister Hannah said they used to watch Project Runway together and it just "seems crazy" she would be watching him on screen.
"I am really proud of Sean, he has always gone the extra mile to get ahead, especially when getting the internships with Henrik Vibskov in Denmark and Alexander McQueen in London," Hannah said.
Head of physical education at Hawera High School Pauline Hurley said Sean did not study fashion at school.
"It just goes to show that sometimes it's not your school qualifications that lead you to success but your passion and drive to achieve in what you choose to do with your career," she said.
Sean is off limits to media during filming of the series.