Gwen Stefani and Gavin Rossdale’s divorce was finalized almost a decade ago, but apparently he hasn’t gotten over it. “Gavin is still stewing over the breakup, so he likes to stir the pot whenever he can,” a source exclusively tells Life & Style. “He heard that Gwen and Blake [Shelton] are going through a tough time right now, so he’s using it as an opportunity to push Gwen’s buttons when he sees her. Gwen doesn’t even like doing the kids’ handoff with him, because Gavin will say something obnoxious or act weird. That’s why Blake tags along sometimes, because Gwen doesn’t feel comfortable going alone.”

The Bush rocker, 58, never wanted his marriage to Gwen, 54, to end, according to the source, “but she wanted out, and he can’t get over it. Luckily, the kids [Kingston, 17, Zuma, 15, and Apollo, 10] aren’t suffering. Gavin and Gwen always put them first and hide any tension when they’re around. And Gwen and Gavin would never badmouth each other to the kids. Gwen just wants to keep things as harmonious as possible, but Gavin makes that extremely difficult sometimes.”

Life & Style spoke to Gavin at Desert Smash produced by Brand Innovators at La Quinta Resort and Club on March 4 — and he seemed to want to avoid talking about his ex. When our reporter asked him, “What’s your advice for coparenting?” Gavin simply replied, “None.”