The son of Steve 'The Crocodile Hunter' Irwin has shared a moving note he received from a stranger on Father's Day.
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Robert Irwin uploaded a photo to his 1.1 million Instagram followers of a message written on a napkin, signed simply "Carolyn".
"I want to acknowledge your beautiful family on Father's Day!" the note read.
"I'm sure he is proud of all of you!!" it added, followed by a love heart.
Robert, a budding wildlife advocate and television presenter himself, explained how much it meant to him to hear from fans of his late father.
"Our lovely flight attendant just handed us this note on our way off the plane..." he captioned the image.
"Little gestures like this really mean a lot. It warms my heart to see people who take a little bit of time to do something kind. Thank you Carolyn."
The 15-year-old photographer celebrated Father's Day with an old photo of him and his sister Bindi Irwin alongside their dad when they were little.
"You'll always be the best dad in the world," he wrote.
Bindi echoed her younger brother's sentiments with a similar post, captioned: "Thank you for always teaching me to stand up for what I believe in. I'm incredibly blessed to be your daughter and I love you so much".