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The couple shared the happy news in a post Erin wrote on their blog titled "Our secret."
That's a fitting title, too, given that they've managed to keep the news under wraps for quite a while.
"I am now almost 7 months pregnant, and it has been thankfully a healthy and easy pregnancy," Erin revealed. "The long hours of filming have been hard on my very tired body each day, and in the first trimester there were headaches daily but never morning sickness. I thanked God for it, and still do."
But that wasn't the only big announcement they made. Now that the "secret" is out, Erin went on to share more details about their baby-on-the-way.
"She’s a girl and we will name her after my grandmother," she wrote. "My prayer for Helen is that she will be brave and kind. I pray that she will not be bullied the way I was, and that she will be a protector of the ones who are. I pray that she will learn that from her father, the protector who loves the people in his life so well."
As for why they waited so long to open up about the baby news, Erin explained that the answer is a simple one.
"We’ve kept it a secret because it felt too close and too important to share," she continued.
But their fans will still get a chance to catch up on the couple's joy during the early days of her pregnancy.
"I’ve not written about it here, but you’ll be able to follow along with our whole journey when season 2 airs."
Season 2 of "Home Town" will premiere Jan. 8, 2018 on HGTV.