The two new babies are Zolciak and the Atlanta Falcons defensive end's third and fourth children together, as Zolciak gave birth to their second son Kash in August 2012 and had their first son "KJ" Kroy Jagger in June 2011.
Zolciak also has two daughters from a previous relationship, 16-year-old Brielle and 12-year-old Ariana, whom Biermann recently adopted. Now, with the twins in the mix, Zolciak and Biermann have six children.
"We are officially the 'Biermann Bunch' now!" Zolciak captioned her Instagram post.
The couple announced Zolciak, 35, was pregnant with twins in August and admitted they hoped to have a daughter. Biermann apparently wanted a baby girl of his own since Brielle and Ariana are older now.
"I'm having twins and I couldn't be more excited. I was completely shocked. I had no idea. It was a natural conception, but twins do run in the family, so I guess I shouldn't have been surprised," Zolciak told E! News at the time.
"I can't believe I am going to be a mom to six children. It's going to be very busy but it's a dream come true."
Zolciak reportedly discovered she was expecting again after taking over a dozen at-home pregnancy tests, which was featured on Don't Be Tardy's second-season finale in June.
Zolciak and Biermann tied the knot in November 2011 after getting engaged the prior month.
(Photo credit Bravo)
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