On Thursday, Aug. 22, the singer, 54, shared a Reel on her Instagram filled with sweet throwback ... Rossdale had the crowd sing "Happy Birthday" to him in honor of his 16th birthday.

"Happy sweet ... last 16 years," he continued. "We are so proud of the person you are and what you stand for. Don't ever change that!! We love u more than you will ever know. Happy birthday ...