The country stars revealed the singer and her husband Chris Tyrell are expecting a sibling for their four-year-old daughter Eisele, and the guitarist and his wife Kelli Cashiola - whose son Cash turns three next month - will welcome a daughter into the world later this year.
They posted: ''Well, #BabyBellum round 2 is on the way!
''We're thrilled to announce the Haywoods are welcoming a girl this December, AND the Tyrrells are expecting in February 2018!!''
The 'Need You Now' hitmakers accompanied the post with a photo of Eisele, Cash, and 18-month-old Ward, the son of third band member Charles Kelley and his wife Cassie McConnell.
Hillary previously suffered a miscarriage in 2015, and afterwards she penned a song, 'Thy Will', based on her experiences in the hope she could offer comfort to others who had been in a similar position.
She previously said: ''I wrote the song in the middle of experiencing everything that comes with the miscarriage so it was my most raw place that I could've ever been when this song truly poured out of me.''
And the 31-year-old singer admitted the tragic loss had made her a ''different'' parent to little Eisele.
She said: ''I'm a different mom to [my daughter] now. I hug her a lot tighter.''
The band are currently on tour promoting their latest album 'Heartbreak' and have spoken in the past of enjoying taking their kids on the road with them.
Hillary said earlier this year: ''We did the tour to Europe when Eisele was a little over a year old and it was the longest we were ever away [from her].
''I swore I would never do it again. So she'll be with us, pretty much everywhere. The world spins right when we are all together.''
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