Garth Brooks' daughter gets engaged after singing back-up at his concert on 21st birthday

It was an eventful 21st birthday for country singer Garth Brooks' daughter, who was serenaded with the "Happy Birthday" song by fans at her dad's concert, and then got engaged backstage just moments later.

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Allie Colleen Brooks began her big evening by joining her dad on stage as a back-up singer during his concert at The Forum in Los Angeles over the weekend.

"Garth Brooks' back-up singers are the best, they've been around for a long time, singing with him 25 years or more," Hunter Kelly, senior correspondent at Rare Country, told "I could tell she really had to have been studying and rehearsing to get up there."

Kelly, who shared videos from the concert on social media, said the country artist didn't introduce his daughter by their shared last name until he invited her to center stage and asked fans to sing "Happy Birthday."

"It was a really cool moment for her to step in there," Kelly said. "You could tell it was emotional for both of them. He had to be so proud of her."

After Allie thanked the audience, she went backstage, where she was met by her boyfriend, Jonathan Roberts, who dropped down on one knee to propose as Brooks played his 1995 hit, "She's Every Woman."

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"I'm beyond blessed to have this beautiful woman in my life," Roberts wrote in a post on Facebook. "She's anything but typical. She's so unpredictable."

Fans later found out about the engagement when Roberts posted videos to social media of their engagement.

"It seemed like a really cool 21st birthday," Kelly said.

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