Pakistan, Aug. 23 -- Gwen Stefani is celebrating her son Zuma Nesta Rock Rossdale's new milestone. The middle child, whom she shares with her ex-husband Gavin Rossdale, officially becomes an adult now as he turned 18.

On Friday, August 21, the No Doubt star took to her Instagram to post a heartfelt birthday tribute, making her son's special day more memorable.

Alongside a dedicated sweet video montage, the doting mother penned an emotional message.

"Happiest 18th birthday Zuma. I cannot believe you are 18 today!!" the Just a Girl hitmaker wrote. "Watching u grow into the sweetest + most talented young man has been one of the greatest gifts of my life."

"We love you so much Zuma," she added before completing the message with a row of f...