He and his sister, Clara Loughran, are no strangers to royalty.
Nick sang at the wedding of Prince Harry and Meghan Markle in 2018, and recently performed at a private service for the Queen on Easter Sunday.
And Loughran, who now works on a freelance basis for the Duke and Duchess of Sussex's charity projects, has worked for the Royal Family for several years.
Their parents have never really got used to their children's proximity to the Crown.
"We sort of think it's wild, it's gobsmacking stuff, you're pinching yourself," Madden said yesterday.
"They accept that they're in a privileged position, they love what they do, and if there's something that needs to be done, like good Kiwis they get on and do it."
The proud parents stayed up into the wee hours to watch the service live.
"We had sweaty palms," Madden admitted.
"But he's just great, he loves it," Madden said.
Their son initially told them that he would be performing early last week.
"We had phone calls during the week, they had pretty intensive two five-hour rehearsals on Thursday and Friday."
He was feeling a little nervous ahead of the performance, but rose to the occasion.
"When you're singing for a potential audience of a million people, you have to have nerves of steel.
"He's great like that, he just gets up and does it."
Nick was one of two Kiwis to take part in the funeral.
New Zealand's Defence representative Lofty Hayward was seen on camera wearing a kahu huruhuru (Maori cloak) as he waited for Prince Philip's custom-built Land Rover hearse to arrive outside St George's Chapel.