The celebrity couple are Australian, but are raising their daughters -- Sunday, 4, and Faith Margaret, 2 -- in Tennessee, which makes for some interesting accents, People reported Friday.
"They have a mix of Australian and southern accents which is really cute," Kidman said during a Friday appearance on "The Ellen DeGeneres Show."
"My mum always says, 'I can't understand her,' because [Sunday's] like ... 'Hey, y'all' to her grandparents," she said.
Kidman said Sunday has picked up her father's love of music.
"She has really good pitch. I'd love it [if she sings]," Kidman said. "The great thing about being married to a musician is you have music in the house all the time. [Keith will] play the piano at 7 a.m. ... we have breakfast around the piano."