Gwen Stefani and Blake Shelton seem happier than ever — but there seems to be one person who isn’t too pleased with their relationship!

According to a new report, Gwen’s ex-husband Gavin Rossdale is bothered that his ex’s new man spends so much time around their kids — Kingston, 10, Zuma, 7, and Apollo, 2!

“Gavin doesn’t agree with [Gwen] having a relationship with Blake, and he doesn’t like her bringing the kids around him,” an insider explains.

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It’s allegedly been hard for the Bush rocker, 50, to see Gwen, 46, with another man — especially since “if it were up to Gavin, he would want to work it out with Gwen,” another source notes.