Jessica and Erin Johnson already share children Maxwell, 6, and Ace, 5.
Last week the country singer and actress took to Instagram to share the happy news.
"We couldn’t be happier to announce this precious blessing of life," she wrote.
Despite Jess being a singer, actress, fashion designer and makeup mogul, being a mum is her favourite role.
"The most rewarding part of being a mother is really just watching my kids grow," she previously gushed.
"it is like, how much knowledge they have about life is just so meaningful to me, and how much heart they put into everything they do. There's just nothing like the innocence of a child."