Josh and Anna Duggar with their daughter Mackynzie and son Michael. Credit: TLC/Scott Enlow

19 kids -- plus now three grandkids! -- and counting! 19 Kids and Counting's Jim Bob and Michelle Duggar are set to be grandparents for the third time: The TLC couple's eldest child Josh, 25, is expecting his third child with wife Anna. A rep confirms to Us Weekly that Anna, 24, is pregnant.

Married since September 2008, Josh and Anna are already parents to daughter Mackynzie, 3, and son Michael, 21 months.

"So thankful for the blessing of our 3rd child!" Josh tweeted after the couple announced the big news on TODAY.

Josh's parents Michelle, 46, and Jim Bob, 47, welcomed their 19th child, Josie, back in December 2009; Michelle suffered a miscarriage in 2011.