Keith Urban and Nicole Kidman’s oldest daughter, Sunday Rose, was born on July 7, 2008, and the country superstar took to Facebook to share a throwback photo of Daddy and "Sunny" on her 8th birthday.

Kidman also shared a photo on Facebook, showing her with a slightly older Sunday Rose. “You bring so much sunshine to our lives,” she writes. “Love Mummy & Daddy xx.”

Urban’s message to his daughter is similar. Younger sister Faith Margaret was born in late 2010 via surrogate. They're the only two kids the couple has together, although Kidman has two older children (Isabella and Connor) with actor Tom Cruise.

The lives of both girls have remained mostly private, despite their celebrity status in the United States and Australia. Urban doesn’t talk about the girls much, and when he does, he doesn’t dive too deeply into detail about what they’re interested in or how they’re raised. If there is a photo, it’s often of a tabloid nature, with one or both girls in their parents’ arms or holding Mum or Dad's hand.

It's not clear if Urban will celebrate Sunny's birthday with her. His Ripcord Tour begins the first of two shows in Toronto on Friday (July 8). The couple are known for working hard to recognize important moments, even if it means just flying in for a few hours or days.  Urban and Kidman celebrated 10 years of marriage on June 25. They weren't able to be together at that time, although Urban did attempt to Facetime his wife.

His latest single is "Wasted Time," which has spent its second week at No. 1 on the Billboard airplay chart.

Keith Urban Turns a Fan Into a Rock Star