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TORONTO — The Toronto Zoo’s twin giant panda cubs are brother and sister.

The zoo announced the genders of the fluffy animals Friday, and released a new photo of the panda siblings.

Figuring out their gender wasn’t an easy task — zoo staff swabbed their tiny mouths for cheek-cell samples, which was then driven to forensics experts at Trent University east of Toronto for testing using DNA sexing protocols developed by the Smithsonian Conservation Biology Institute.

The news opens the door to naming the cute little bears — and the zoo is teasing a “special announcement” on Monday.

The nearly four-month-old panda twins were born 13 minutes apart and have yet to make their first public appearance, remaining behind the scenes in the panda exhibit’s maternity area with their mom, Er Shun.

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Zoo officials says they’re hoping to reveal the panda pair in mid-March.

WATCH: The Toronto Zoo released footage in January showing just how big a giant panda cub has grown after 12 weeks.

0:35 Sleepy 12-week-old panda caught yawning at Toronto Zoo Sleepy 12-week-old panda caught yawning at Toronto Zoo