Angelina Jolie and Brad Pitt usually keep their twins well hidden.

PHOTOS: Angelina And Knox Play Peek-A-Boo!

But as RadarOnline.com discovered in Venice, Italy, that cover can be blown with a game of peek-a-boo!

PHOTOS: Johnny And Angelina Film The Tourist

On the private balcony of the 15th century penthouse that the Brangelina clan are renting while mom films The Tourist, 20-month-old Knox appeared to relish the view from above.

PHOTOS: Angelina Jolie's Daughter Cries For Mommy

There was no sign of twin Vivienne.

But as they grow older, the blond and blue-eyed twins -- the youngest kids among the Jolie-Pitt six -- continue to look more and more like their big sister Shiloh, who also showed her face during the fun games!

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