Facing Bindi, he said: “It was just so sweet of you to think of me to do that... I'm nervous, I'm not going to lie. There's a lot of pressure!”
“But I love Bindi and Chandler so much and together I know they'll achieve so much,” he added.
Chandler, who proposed to Bindi last year on her 21st birthday, enlisted the photographic skills of Rob, who was hiding in the bushes at the time, to capture the moment on film.
Rob’s candid confession about Bindi’s wedding comes after he shared some big news of his own earlier on in the week, when he announced he has got his learner driver’s permit.
“Here we go! I’m so excited to finally start driving... and happy to be learning in the best car - Dad’s old Ute!!” Robert wrote.
Many of Robert's fans and supporters took to Instagram to comment on the snap, with one fan writing: “Congratulations! What an honor to have your Dad’s Ute!”
Another fan stated: “Ya look like a natural, you really do look like your dad but I see your sweet mama lurking around there too. Handsome young man.”
While celebrity mate Blue Wiggle star Anthony Field wrote: “Awesome Robert! When you are qualified, come and take the big red car for a son!”