Tim McGraw and Faith Hill can notch another milestone in their well-traveled journey. Their second daughter, Maggie, is celebrating adulthood Monday (Aug. 12) as she blows out 21 candles on her birthday cake!

McGraw posted a sweet tribute to Maggie on Instagram, noting how much she means to their family, "Happy 21st to our Maggie May!!! Your mom, sisters and I are so very proud of you," he wrote, alongside a medley of pretty photos of the birthday girl. "All of your adventures and passion for life is infectious! Don’t ever stop being willing to learn. Your mother and I never tire of your eagerness. We are SO very fortunate to have you and your sisters in our lives!!! Let’s get out there and make some more memories!"

Mom Hill posted her own tribute, choosing to flash back three years to a video of herself and the birthday girl singing loudly to Mark Ronson's "Uptown Funk" in the car.

Maggie is the middle child in between big sister Gracie and little sister Audrey, and has the distinction of very clearly looking like both of her parents, arguably more than either of her siblings.

Eldest sis Gracie turned 22 i n May, and is notably blessed with her parents' singing talent: She joined her father on "Here Tonight," a duet from his Damn Country Music album, and even sang it onstage with him at his Nashville tour stop in 2015.

Meanwhile, the baby of the family, Audrey, turned 17 in December 2018, and is on track to all-too-soon make her parents empty-nesters.

Don't Miss These Summer 2019 Country Music Festivals!