The youngest member of the McGraw-Hill family is growing up. Tim McGraw and Faith Hill celebrated their daughter Audrey's 21st birthday on Tuesday (Dec. 6) with separate posts sharing stories and memories about the youngest of their three girls.

McGraw kept things sappy and sentimental in his post, sharing a photo montage set to "My Little Girl," a tender ballad he released in 2006. Audrey was born in 2001, so it's likely the country superstar had her — and his two other daughters — in mind when he wrote and recorded it.

"Our baby gurl turns 21 today!!!!" the singer writes in the caption of his post. "We r so proud of the remarkable young woman you have become ... U make this world a better place to be for everyone who loves you. Happy birthday 'my little girl.' We love you so much!"

Audrey and her two sisters inherited their parents' musical talents: All three can sing, and Audrey occasionally shares covers of other artists' songs on her social media, such as a recent take on Pat Benatar's "Fire and Ice." She also starred in the music video for her dad's song, "7500 OBO."

In her birthday tribute, Hill chose to reminisce about her daughter's birth story, with a lengthy caption set to video of Audrey dancing at a concert.

"Coming into this world almost 8 weeks early with the widest smile on her face and the biggest eyes," Hill remembers. "I will never forget looking right into those eyes staring back at me saying, 'What cha'll worried about, I'm ready to go ... let's get on with it!!!'

"That spunk and spirit put me right at ease," Hill continues. "I knew Audrey Caroline McGraw was going to be just fine. She came early for a reason and she was ready to prove it!!!!"

Audrey was also on the receiving end of a humorous birthday message from her oldest sister, 25-year-old Gracie.

"You were the cutest baby in the world and now you're a hot, intelligent, poignant b--ch," Gracie writes. "It is rude to be hotter than your older sister, but I love you, so I don't mind. I'm so proud of the work you are doing and the work you are striving for. You will do great things my little chicken."

McGraw and Hill celebrated their 26th wedding anniversary in October.

See Tim McGraw and Faith Hill's Best Pictures Together Through the Years

Tim and Faith's Most Unforgettable Moments

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