Bindi Irwin has grown up in front of the world over the years, and so has her brother Robert Irwin! The son of the late "Crocodile Hunter" Steve Irwin celebrated a milestone birthday on Wednesday as he turned 18 years old, and Bindi made a special Instagram post to honour the occasion!

Bindi says she'll "always, always be there for" her brother

Bindi posted a photo of her and Robert at the Australia Zoo that was taken during her March 2020 wedding to Chandler Powell. In the picture, the two siblings can be seen posing together while smiling at one another, with a giraffe seeming to stare at the camera from behind them. "Forest’s face behind us says it all… happy 18th to the very best," Bindi began her birthday tribute.

Since she and Powell welcomed her first child in March, she also mentioned Robert's new role within the family. Bindi said he has "been promoted to uncle and taken on the world" in 2021, expressing how she "can’t wait to see what incredible adventures are on the horizon" for her little brother. She concluded her message on a sweet and humorous note! "I’ll always, always be here for you (with a fully stocked fridge)," she shared, sending him love.

The children of the late Steve Irwin: Bindi Irwin and Robert Irwin 

Powell also made a special post for Robert's birthday! He shared a photo of them sitting outside with his daughter, calling Bindi's brother "Grace's Funcle" and writing a thoughtful message of his own. "A birthday filled with feeding crocs and surfing is the perfect way to kick off your 18th lap around the sun," Powell wrote on Instagram, thanking Robert for making day-to-day life at the zoo "an unexpected adventure."