Robert Irwin has shared a heartwarming letter he received from a stranger.
Steve Irwin's 15-year-old son was travelling on a plane on Fathers day in America when a stranger walked by and passed him a paper note.
"Our lovely flight attendant just handed us this note on our way off the plane,"
"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 note said:
I want to acknowledge your beautiful family on Father's Day! I'm sure he is proud of all of you!
Robert paid tribute to his father Steve, on Instagram earlier that day with a gorgeous picture of him, Binidi and his late father.