Kevin Mazur/WireImageBlake Shelton celebrated a milestone birthday Saturday as he turned the big 4-0. His girlfriend, Gwen Stefani, was right by his side.
The two celebrated by performing their duet "Go Ahead and Break My Heart" at Country Jam in Grand Junction, Colorado. Gwen surprised concertgoers by hopping onstage at the end of Blake's two-hour performance.
Gwen retweeted a fan's video of her surprise appearance Saturday night.
She captioned one boyhood photo of Blake on Twitter: "Happy birthday to my favorite person I ever met @blakeshelton gx #superbabe."
Gwen also took to Instagram to share another throwback photo of Shelton, with the caption: "Happy birthday to @blakeshelton literally my favorite person gx."
In addition to the older photos, she posted a current photo of herself blowing a kiss to the birthday boy.
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