The 50-year-old actor says she and Witherspoon, 41, have a lot in common.
"We have so much in common. We both started work really young, and both our mothers were nurses and we've had similar experiences at different times of our lives - I see her as a little sister," Kidman says.
The actor adds that they both own beach houses in Bahamas and love to hang out with each other during family vacations.
"We're actually next-door neighbours. I'm on my balcony and I'm like, 'Hi baby'.
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