BINDI Irwin, the daughter of Crocodile Hunter Steve Irwin, has revealed how her brother was in on her surprise marriage proposal on her 21st birthday.

The 21-year-old Sunshine Coast animal lover and wildlife warrior tweeted beautiful new pictures of her marriage proposal by boyfriend Chandler Powell at Australia Zoo.

"The most beautiful surprise. Chandler & Robert worked together to capture the moment I said 'YES' in the gardens of Australia Zoo,'' Bindi gushed in the post.

"Beyond perfect. I never knew Robert was there photographing & I'll always be grateful to have these special memories of the best day of my life."

The tweet was met with responses from around the world including in the US, where the Irwins are hugely popular.

"I dont know why it tickled me so much, the thought of someone getting proposed to and their brother is hiding in the bushes taking pictures. But it did. Lovely shots though,'' one tweeted.

"Big congratulations both of you!!! I knew it.  You both are perfect couple! Your dad so proud of you!! I was there to watch you with five other contestants at DWTS from studio audience in LA around few years ago.  That's amazing.   Again, congratulations!"

Another wrote: "I am so incredibly happy for you. I am so glad to see you happy, your father and your family inspired me to do the work I do. Working with endangered animals every day is amazing and I may have never achieved it without him. Go Bindi! So proud and I know your father is too."

Bindi first posted the happy news on Instagram last night, sharing a photo of her stunning engagement ring.

"July 24th 2019. On my birthday I said 'yes' and 'forever' to the love of my life," she captioned a photo of the couple.

"Chandler, close to 6 years ago I fell in love with you and every day since has been a whirlwind of adventure and true happiness.

"I'm so looking forwarding to spending our forever together as your wife. Here's to a lifetime of friendship, purpose and unconditional love. - Now let's get married already!"

The couple were flooded with wellwishers, with Bindi's brother Robert commenting a series of love heart emojis.

Chandler, 22, also shared a post celebrating their engagement, revealing he had proposed to Bindi at Australia Zoo.

"She said YES! Almost 6 years ago we met at Australia Zoo. I immediately fell head over heels for her kind and thoughtful heart that radiates so much light.

"Proposing in her very favourite place in the zoo, surrounded by animals, seemed like the perfect way to embark on this incredible new chapter in our lives. Bee, I love you more than anything in this world and I always will. Happy Birthday."

Proud mum Terri also shared her well wishes for the couple on Twitter, revealing she was "so very happy, and I know Steve would be too".

Chandler had been by Bindi's side as she celebrated her 21st birthday at Australia Zoo.

The couple looked smitten as they posed for photos together.

- with news.com.au