Things look to be going swimmingly for not only Gwen Stefani, 50, and Blake Shelton, 44, but for his relationship with her three sons Kingston, 14, Zuma, 11, and Apollo, 6 (who she shares with ex-husband Gavin Rossdale, 54). “Blake is a fun guy who is completely natural with Gwen‘s kids,” a source revealed to HollywoodLife EXCLUSIVELY.