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Matthew Broderick's 6-year-old son, James Wilkie, can't wait to meet his twin sisters.

"He's pretty excited," Broderick tells David Letterman in an episode of the Late Show airing tonight on CBS. It's his first interview on the babies since he and wife Sarah Jessica Parker announced they were expecting via a surrogate last week.

See photos of stars with twins.

"He said, 'We have to get a lot of princess toys,'" Broderick says. "He's just now thinking, 'Wait a minute, am I [not going to be an only child anymore]?'

"He's a pretty grown up kid," continues Broderick.

See Us' baby bump hall of fame.

Broderick jokes that he's not as confident about raising twin girls.

"Oh man, I'm nervous just even thinking about it," he says.

Letterman asks: "Are you ready for this? Because...it's not just one child, it's, like, two. It's like one of those Octo-mom deals."

See photos of stylish moms on the go.

"Yeah, I'm ready. You know, I've asked people, 'What's it like to have twins?' One father said, 'I don't recommend it,'" quips Broderick -- currently starring in The Philanthropist on Broadway. "But the rest have been very positive."