The Robertson family is rapidly expanding!

Just two days after her daughter, Rebecca Lo Robertson, announced her engagement, Korie Robertson told fans that she wouldn't just have a new son-in-law but also another son.

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The "Duck Dynasty" star and her husband, Willie Robertson, are in the process of adopting a 13-year-old boy. Korie posted a photo of her growing brood to Instagram on Sunday, answered the question many fans were asking: Who's the cute kid that keeps popping up in their photos?

"We are excited to be in the process of adopting a new son!" she wrote. "He's been with us since May, but we wanted some privacy and time for him and our family to bond before telling the world (It's a bit of an adjustment coming into this big, crazy family, ha��)."

"He's amazing, and we are all so thrilled to have another kid around the house," the 42-year-old reality star added.

While she didn't share her soon-to-be-son's name, Korie did admit that the family "couldn't keep the good news to ourselves any longer!"

The Louisiana native is very excited about the new addition to her family, filling ET in on how he's already been made a big part of the Robertson household.

"We got him in May, at the end of the school year," Korie told ET. "He was at John Luke's wedding and walked my grandmother down the aisle."

Korie and Willie are already parents to five children -- their three biological kids, John Luke, Sadie and Bella, an adopted son, Will, and a foster daughter, Rebecca, who first came to the family as an exchange student from Taiwan in 2004.

ET spoke with the couple in November, and they shared their different parenting methods for each of their children.

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"Some of our kids are one way, some of them were hard-headed, some of them were not. Some of them were super sensitive, so you have to take all of that into effect," Willie told ET. "I could look at Sadie one way, and she would start cryin' -- like that! -- it wasn't a spanking or anything like that, she was so sensitive. And John Luke was very hard-headed, and his brother, Will, was very hard-headed."

We'll see even more of their parenting skills when "Duck Dynasty" returns to A&E on Jan. 13.