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When Kim Zolciak tweeted that she was making a "VERY exciting and personal announcement," she wasn't kidding.

The "Don't be Tardy" star, 35, and her husband, Atlanta Falcons player Kroy Biermann, 27, are expecting twins, she announced today.

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"I'm having twins and I couldn't be more excited. I was completely shocked. I had no idea," she told E! News. It was a natural conception, but twins do run in the family, so I guess I shouldn't have been surprised."

Zolciak, a Bravo star who first appeared on "The Real Housewives of Atlanta," is already the mother of four children, including two sons, Kroy Jr., 2, and Kash Kade, 9 months, with Biermann. (The NFL player also adopted her daughters, Brielle and Ariana, from previous relationships.)

"I can't believe I am going to be a mom to six children," she said. "It's going to be very busy but it's a dream come true."