Bindi later revealed she didn't hear from Chandler for a few weeks after their first meeting, due to him waiting for her mother Terry's permission.
"He sent a letter asking my mom if he could stay in contact with me," she told ET, "and then mom gave the letter to me and said, 'Is this person real?'"
E! News reported that they dated long distance for a while after that, which wasn't easy for the couple.
Bindi's brother, Robert Irwin, also told People that he wanted to "test" Chandler first, to see if he could fit in with the family of animal lovers.
"One of the first times Chandler came to the zoo I wanted to kind of test him," Robert said, "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."
Chandler fit the Irwin family like a glove, even jumping on a crocodile in 2017.
"He actually just came on our annual crocodile research trip," Bindi told E!'s Daily Pop at the time. "The ultimate test was saying, 'Now you're going to jump on top of a 15-foot crocodile.'"
Bindi also claimed that Chandler was a support for her while she was on Dancing With The Stars, travelling to Los Angeles to for her tapings.
She thanked him in an Instagram post for "helping me to ice my foot when it hurts, making me tea and hugging me when I'm tired. You're amazing."
He also surprised her by coming to a practice session on his birthday, with the help of her dance partner Derek.
"She was like, 'Oh my gosh, what are you doing here?' and she starts fixing her hair…it was so cute to see," Derek told E! News backstage at the time.
"It was so much fun," Bindi said. "And it was Steve Irwin Day as well, so I got the two greatest days. We got to celebrate Chandler's birthday and then celebrate Steve Irwin Day altogether. It was really, really nice."
In 2016, Terri Irwin said she believed Chandler was the one for her daughter, and said Steve would've been "happy" their daughter was dating him.
"I think because Chandler's a nice person and really kind to Bindi that he'd be very happy," she told E! News at the time. "What's kind of ironic is I was talking to Chandler's mother, and he was an avid Crocodile Hunter fan when he was little. So he used to put on the big khaki shirt and go to school when he was in first grade and pretend to be Steve."
Chandler finally moved to Australia in 2018, and lives with the Irwin family at the Australia Zoo.
"I've got my khaki on and I am loving it!" he told People at the time.
The couple also appear together on the Irwin family's Animal Planet series, Crikey! It's the Irwins.
"Beautiful Bee, I love you so much," he posted the day before he proposed. "You're my best friend and whole world. I can't wait to celebrate your birthday tomorrow at #AustraliaZoo. Here's to another year and beyond of life changing adventures together."
Chandler proposed to Bindi on her 21st birthday, with a ring that proved just how well he knew her.
"Chandler was incredibly thoughtful when he chose it," Bindi said. "The ring captures the essence of who I am (with its vintage flare) and our life together, with the twisted band and scattered diamonds."