Dancing's Maks: My Kids with Karina Will 'Be Rock Stars'
"Planning the proposal was the most nerve-wracking thing of my life," the dancer, 29, tells PEOPLE in its new issue. "When it came down to it, I thought, 'It's not a given that she'll say yes.' All of a sudden it's like, 'I have nothing to say! Why did I even do this?' "
Adds Smirnoff, 31: "I thought it was so cute because you never see Maks [nervous] like this."
Although they only started dating in late September, the Ukrainian-bred couple – who will square off against each other in the new season of DWTS, debuting March 9 – actually have a long history: They first met as teenagers on the pro dancing circuit.
"You know how boys tend to develop slower than girls?" asks Chmerkovskiy. "A lot slower!" says Smirnoff. Back then, she adds, "I never looked at him seriously."
Now the couple, who plan to wed in late 2009, are looking ahead to starting a family. "Our kids would be rock stars," says Chmerkovskiy, playful swagger back in place. "They're going to be like royalty."
For more on this story, pick up the new issue of PEOPLE, on newsstands Friday
Maks had 'difficulty forming sentences' says Karina of his proposal