Will Josh and Anna adopt?

Since Josh's sister Jessa and her husband revealed their adoption hopes, and his sister Jill, 23, and her husband Derick, 25 – who are expecting a baby boy in weeks – also said they were interested in adoption, will Josh and Anna go down the adoption path as well?

"We've been married long enough," says Josh, who married Anna in 2008. "We have talked about it, and we've discussed it with Jessa and Ben and Jill and Derick. But it's not something we are planning right now."

But, he says that he believes adoption is important and not something he and Anna would rule out.

"Every person has to make the decision for themselves and adoption is the loving option," he says.

For now, the couple is grateful for the children they have – and the one they're going to have, Anna says.

"Some people think I'm not happy unless I'm pregnant," Anna says. "Marcus just celebrated his first birthday and I was thinking, 'My baby is growing up.' There is a desire to have more children, but also keep the balance of enjoying what God has given you and enjoy the children we have."

For Josh, his growing family is teaching him about patience and grace, he says.

"If someone told me when we got married, I'd have three kids and one on the way, I'd have been overwhelmed," he says. "As you go along and have more children, there is just enough patience and grace."

Says Anna, "It's definitely busier the more you have. But it is a happy busy. There is no better way to invest my life, my body and my time than to my children. They are a huge responsibility and a blessing. And all good things in life require work."