Panda twins celebrate birthday at Zoo Atlanta

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A big birthday is happening Tuesday at Zoo Atlanta.

The zoo's twin panda sisters Ya Lun and Xi Lun are now 3 years old.

The bears celebrated with some new toys shaped like birthday cakes.

These pandas are more than just cute, they're special.

They're the only giant panda twins in the United States.

Ya Lun and Xi Lun were the sixth and seventh offspring of Lun Lun and Yang Yang, who arrived at the zoo 20 years ago.