The newly crowned Sky Arts Portrait Artist of the Year, who stepped up to his easel and beat 54 other artists to win a £10,000 (€11,500) prize, discovered through the show that he is actually related to his subject.
After meeting Mr Norton for the first time to begin painting his portrait, he found they share family from Ballymena.
Mr Reid’s great-grandmother is the sister of Mr Norton’s great-grandfather.
“I still can’t quite take in the chances of me, out of all the people who entered, getting the opportunity to paint Graham, out of all the people they could have chosen and it turning out we’re third cousins,” said Mr Reid.
“My dad knew there was some connection a while back but only decided to tell me about a week after the final when we were in Kerry together.”
Some of his cousins thought there was a connection after Mr Norton featured in the BBC’s television series Who Do You Think You Are? in which celebrities trace their ancestry.
Mr Norton said it is a huge honour for him to have his portrait displayed in the National Gallery of Ireland.
“I apologise to the artist and the visitors to the gallery, but a combination of vanity and my mother’s excitement meant I couldn’t refuse,” he said.
In the final, Mr Reid, who is from Belfast and now lives and works as an artist in Glasgow, demonstrated his skills on the show with two paintings.
He created a finely detailed portrait of actor Tom Courtenay using charcoal, watercolour, pencil, and pastels.
The other painting was a commissioned portrait of Judge Cheema-Grubb, the first Asian woman to serve as a high court judge in Britain.
Mr Reid won his heat in week six of the show with his portrait of TV presenter Adrian Chiles, before again impressing the judges in the semi-final with his portrayal of award-winning actress Imelda Staunton.
The other finalists were London-based US artist Kimberly Klauss and Lancashire’s Liam Dickinson.