"Some of you have guessed, some of you had no clue... November, 2019 Baby Forsyth #2 is Due!" the couple wrote on their joint account.
"Cannot wait to meet this new little one! Gideon is going to be such a great big brother!! #baby2due #babyforsyth #pregnant."
The couple's son, Gideon Martyn Forsyth, is 14 months old. He was born weighing over 10 pounds on February 23, 2018.
"Our favorite math is addition and we are very excited to share that the Forsyth family is adding a member!" the pair said in a media statement obtained byPeople.
"Marriage and being a mom and dad to Gideon has already far exceeded our expectations. We are looking forward to loving another little one and seeing what special dynamic he or she brings to our family. Table for 4 sounds perfect!"
The Duggar clan also took part in sharing Joy-Anna and Austin's big baby news on their family's website.
"The Bible is right, there is no greater JOY than seeing your children walk in truth," said Joy-Anna's parents Jim Bob Duggar, 53, and Michelle Duggar, 52.
"We have loved watching Austin and Joy build their lives together as a married couple and as parents. Their love for God, each other, Gideon, and others is genuine and inspiring. We could not be more thankful as we watch their lives unfold day by day."