The 'All Night Long' musician explained that 4-year-old granddaughter Harlow and 2-year-old grandson Sparrow had never seen their grandfather on stage until he duetted with their father Joel Madden during The Voice Australia's finals on Sunday (June 17).
Richie told the Courier-Mail: "While we were singing, I could see [daughter] Nicole with Harlow and Sparrow out of the corner of my eye, and it dawned on me they have never seen me on stage before.
"You just know they were thinking, 'What's Pop-pops doing with Dada?'"
Richie and Madden performed a rendition of 'Easy', one of Richie's biggest hits with his former band Commodores, on Sunday, and the Grammy Award-winning star said that had he been in Madden's shoes, he would have been nervous about singing live on television with his father-in-law.
"Singing with your father-in-law is enough to make you nervous. Singing with your father-in-law in front of your family and a couple of million people at the finale of a show... I would have passed out," he quipped. "It could go all wrong. But it was great."
Richie also confirmed that he intends to return to Australia for more live shows in February 2013.