Gwen Stefani and Gavin Rossdale's children are growing up fast! Over the weekend, their middle son Zuma turned 12, and the pre-teen marked the special occasion in style!The birthday boy enjoyed early celebrations with his famous father and siblings on Malibu beach, and his big brother Kingston shared a sweet photo of them posing on the rocks together on his Instagram account, having re-posted it from his dad's social media page.Proud dad Gavin shared a sweet tribute to his middle child on his