Irwin, who got engaged last month to Chandler Powell on her 21st birthday, penned a letter to her dad that she posted on Instagram detailing what a wonderful person her brother, Robert, 15, has become, while also confirming that he will walk her down the aisle at her wedding.
“Dad, You would be so incredibly proud of Robert. He has been such an amazing support during this beautiful new life chapter. I know you’d be beaming with pride when the time comes that he walks me down the aisle. I wish you could be here for these moments, but I know that your spirit lives on in us,” she wrote.
“I think that for me, it’ll be really important that Robert walks me down the aisle,” she told "Entertainment Tonight." “That’s something that I really want to do.”
Irwin and Powell have been dating for about six years. They met at Australia Zoo, founded by Steve Irwin, which is where the engagement took place.
Irwin has never been shy about expressing what her father means to her. In March, she shared a video of him talking about how much he loved his daughter.
"Every time I watch this clip my heart overflows with emotion. The people we love are always with us. Love lives on no matter what & I think that is the most beautiful thing about our existence Thank you, Dad, this moment captured on camera made my whole life," she wrote.
Last year, she posted another video and referred to him as "my superhero."
"My first time watching this footage was only a few days ago. I don’t think I’ll ever be able to describe the amount of emotion in my heart once the video ended. My dad. My superhero. I promise to do my best to make you proud and ensure your legacy lives on forever," she wrote.