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Bindi Irwin and Chandler Powell are engaged!

The conservationist shared the news on Twitter on Wednesday, posting two photos of herself with her longtime love. In one photo, Irwin and Powell share a sweet hug, while in the other Irwin gives a close-up look at her stunning engagement ring.

“On my birthday I said ‘yes’ & ‘forever’ to the love of my life,” Irwin, who celebrated her 21st birthday on Wednesday, captioned the sweet snaps. “Chandler, close to 6 years ago I fell in love with you & every day since has been a whirlwind of adventure & true happiness.”

“Here’s to a lifetime of friendship, purpose & unconditional love,” she added. 

Irwin tells PEOPLE exclusively, “I am overjoyed to be sharing the news that Chandler and I are engaged! This has been the most special day celebrating my 21st birthday.”

She adds, “I’ve met my soulmate and I can’t wait to spend the rest of my life with Chandler. We’ve been together for nearly 6 years now and he’s my happily ever after.”

Powell, too, tells PEOPLE that the engagement was “the most perfect and beautiful day of my life.”

“After Bindi’s birthday celebration at Australia Zoo, we had a photoshoot organized to celebrate her turning 21,” he reveals. “Just before we started the shoot, I took her to a special part of Australia Zoo to ask the girl of my dreams to become my wife. These past five years together have been the best of my life and we look forward to a lifetime of magical moments to come.”

Irwin’s mother, Terri Irwin also tweeted about the exciting news, writing, “Best day ever! Chandler asked and beautiful @BindiIrwin said yes. I am so very happy, and I know Steve would be too. Congratulations!!”

Irwin and Powell, 22, first met in November 2013 when he was in her native Australia for a professional wakeboarding competition and decided to stop by the Australia Zoo, where the Irwin family lives and works.

“It just so happened that Bindi was giving tours that day,” he recalled to PEOPLE in December. “I’m like, ‘Wow she is amazing.’” The pair “hit it off right away,” he said, adding, “We haven’t looked back since.”

For her part, Bindi told PEOPLE she couldn’t be happier to have found a partner who shares so many of her father Steve Irwin‘s qualities. “He loves wildlife and conservation and he has this strength. Which is necessary when you’re jumping on crocs,” she said.

RELATED: Chandler Powell Loves Life at the Zoo with Girlfriend Bindi Irwin: ‘She Is Amazing’

Powell relocated from Florida to live with the Irwin family, who now star in the new Animal Planet series Crikey! It’s the Irwins.

“I’ve got my khaki on and I am loving it!” he recently told PEOPLE.

“One of the first times Chandler came to the zoo I wanted to kind of test him,” Bindi’s younger brother Robert Irwin, 15, told PEOPLE last winter. “Just to see what would happen. So we had him feeding alligators and he did awesome. I’m very impressed. He’s great with wildlife so I approve.”

RELATED: Why Bindi Irwin Thinks Her Boyfriend Is ‘the One’ — and How She Honors Late Father Steve

The wildlife conservationist also gushed about her longtime boyfriend to PEOPLE in May 2017, and admitted that she is “very lucky” to have him in her life.

“Chandler is the most lovely guy on the planet and I feel very blessed that I found someone who shares my passions in life: wildlife conservation and nature,” Bindi said.

“He’s just always there for me. My family loves him too, which is terrific. And it’s wonderful to find somebody who really will be there no matter what. Chandler is endlessly patient. I think that sometimes, I’m like my dad where I’m not a very patient person, I just want to do everything right now. And Chandler has unending amounts of patience. I learn a lot from him. He’s always so kind,” Irwin told PEOPLE. “I’m really lucky to have found Chandler.”

• By Natalie Stone