The 49-year-old was given just six months to live when he was diagnosed with stage four lung cancer, which has since spread to his brain, in August 2020, and publicly shared his prognosis in November.
Taking to Instagram on Wednesday, the TV star shared a heartwarming clip of his son Rex, three, and two-year-old twins Rafa and Cormac playing in superhero get-up.
His eldest, who was dressed up as Cat Boy from Disney’s PJ Masks, could be seen running onto their sofa while his twins transformed into Chase from Paw Patrol and the Incredible Hulk.
In the video, Irwin asks, “Who are you?” as Rex catapults himself onto the couch and performs a cartwheel.
Responding to his dad, he enthusiastically says: “Cat boy!”
Captioning the post, he penned: “3 superheros under one roof. Im not sure I’ll make the grade!” (sic).
It comes days after Irwin shared a heartbreaking update about his health.
Speaking about his diagnosis, Irwin told The Sun: “I’m weak now, fragile and my memory is terrible… but I’m still here.”
The TV star, who celebrated his 50th birthday seven months early this week, then revealed how living with terminal cancer has impacted his parenting duties.
Irwin recalled how a recent kickabout with his son Rex almost “broke” him due to feeling “weaker” as a result of his cancer.
Jonnie Irwin - In pictures
He explained: “I tried to play football with Rex the other day and was in goal and I couldn’t get near the ball. It was so frustrating.
“I’m very sporty and suddenly it’s just like… it was as if it was the first time I’d attempted football. I felt like a granddad. And that broke me a bit.”
The presenter lives in Hertfordshire with his wife Jessica Holmes, 40, and their three children.