Gwen Stefani and Gavin Rossdale prefer to keep their children out of the spotlight, but the former couple occasionally share pictures of them on social media.MORE: Gwen Stefani's son appears in very rare photo with famous sister Daisy LoweAnd over the weekend, the Bush frontman delighted fans after posted a rare picture with his youngest son Apollo, seven.The sweet selfie showed the pair posing on the beach, and was captioned: "Greatest gift." Gavin's oldest child, model Daisy Lowe, was one of