Lionel Richie talks on granddaughter

Proud grandfather Lionel Richie tells daughter Nicole Richie that not only will her own daughter grow up fast, she'll soon be moving fast, too.

"I call her 'The Mouse'," Richie said of his 10-month-old granddaughter, Harlow, "and The Mouse holds on to the edge of a chair now and is gaining the confidence to think, 'Maybe these legs belong to me.' I keep telling Nicole that it's a bad sign, because once those legs gain confidence, then they're out of here!"

Richie tells PEOPLE he is amazed that his one-time wild-child, Nicole is now a devoted mum with boyfriend Joel Madden.

"I'll be visiting the house," Richie says with a laugh, "and Nicole will be like, 'Dad, lower your voice! Harlow is sleeping!'

"We must be talking about someone other than my daughter! This is not the same Nicole that brings 15 friends over to my house while [Lionel's daughters] Myles and Sofia are sleeping, and says, 'Dad, what's the problem?' "

Adds the elder Richie, "This is whole new territory, and I couldn't be happier."