Sharing a snap of himself leaning against his dad's old ute, on which he learnt to drive, Robert stood beaming and pointing to his fresh new red P plate.
"Passed my driving test! 🎉" the teenager wrote.
"My first solo drive was a super special one - took my dad’s old Ute to see Grace in the hospital right after she was born 😊"
The wildlife warrior was soon flooded with comments of support. And right front and centre was his older sister, and new mum, Bindi.
"So proud of you!!!" she wrote underneath.
Fans were also delighted for the new driver.
"Well done, now you and your dads truck can make new memories." one user wrote.
"Congrats on passing and congrats on being a new uncle!" another chimed in.
Just four days ago Rob shared a different kind of milestone to his Instagram.
Posting a sweet photo of himself cradling his new baby niece, the 17-year-old gushed about his new role as uncle.
"Let the uncle adventures begin!" he wrote.
"Love you so much, Grace ❤️ This little one picked the two best parents in the entire world.
"The most incredible, caring and strong Mum... and the funnest, coolest and kindest Dad.
"Love you three so much - I can’t wait for this exciting journey ahead!"