The Bryan kids are growing up, and like any mom, Luke Bryan's wife Caroline has some mixed emotions about it.

Bo Bryan — the second-to-youngest member of the family — turned 15 years old on Saturday (March 18), and that means that there's one big milestone looming in the Bryan's near future: The day that Bo gets behind the wheel.

"My once tiny baby is officially 15!!!" Caroline writes, waxing nostalgic on social media. "I might need to be medicated this next year teaching him to drive. We love you sweet Bo!!!"

She also shared a spread of pictures in her birthday tribute including one recent selfie of her and Bo where her bewildered-but-happy face says it all. A second shot shows the birthday boy's younger self, and the third slide is a video documenting a family tradition: Bryan jumps on a bed and blares a pumped-up birthday song to wake up Bo on his birthday morning.

Caroline wasn't the only one feeling emotional about the passage of time. In the comments section of her birthday tribute to Bo, Bryan's mom LeClaire chimed in, replying "So getting grown up now. Makes me sad."

Luke and Caroline Bryan are also parents to 12-year-old Tate, and they adopted now-adult nieces Jordan and Kris and nephew Til after their parents — Luke's sister and her husband — died.

In addition to the family birthday celebrations, Bryan has been keeping busy on the latest season of American Idol, where he is a judge. The series airs on ABC.

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