"This photo was taken within the first year of my life," she captioned a picture of herself with her parents. "To be perfectly honest life has changed in a million ways since this photograph was taken."
Steve and Terri married in 1992 and welcomed Bindi and Robert in 1998 and 2003, respectively. The couple gained widespread fame on the TV series "The Crocodile Hunter" before Steve's death at age 44 in 2006.
"Since this photo was taken, 18 years ago, one life ingredient has remained, unchanged, unbreakable. That is the unconditional love that is shared between my beautiful little family and the loyalty we have to each other and everyone else who has taken this journey with us," Bindi Irwin said.
"I don't think that when this photo was taken even my beautiful parents could have known what life would evolve. I know that I am endlessly grateful for the love and light I have been given since Day 1 of my life," the star concluded.
She celebrated her birthday with her mom, brother, boyfriend Chandler Powell and thousands of fans at the Australia Zoo the same day.
The zoo was founded by Steve's parents, Bob and Lyn Irwin, and is under Terri's ownership.
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