When Steve Irwin was just 6 years old ... when he and Irwin were about eight days into filming a series called Ocean’s Deadliest for which they had dived into chest-deep waters near Queensland ...

The couple had two kids, Bindi and Robert, who have continued Steve's work in wildlife conservation. On Sept. 4, 2006, Irwin was killed in a freak ocean accident after being stung by a stingray.

Steve Irwin's children are remembering his legacy. In honor of the late zookeeper's birthday, his adult kids Robert and Bindi Irwin each shared poignant messages to commemorate the significant day ...