Gavin Rossdale is a doting dad to the trio of children he has with his ex-wife, Gwen Stefani, and he delighted his fans when he shared a photo alongside two of them on Instagram.But while the snapshot showed just how much fun Apollo, seven, and Kingston, 15, had been having with their father over the summer, his social media followers pointed out there was someone missing. MORE: Gwen Stefani melts hearts with youngest son after awkward encounter with ex Gavin RossdaleMiddle son, Zuma, 13, was