Steve Irwin's son marks his 21st birthday with a "heartbreaking" admission that he will "never be complete" without his famous father.

Robert Irwin, Steve Irwin's son, continues to feel the enduring grief 18 years after his father's tragic death.

Before turning 21 on November 30, Robert discussed with Australian publication Stellar the emotional significance of this event, the difficulties he has faced in growing up without a father, and how his new TV role is a subtle tribute to his dad.

"It can be heartbreaking to not have a father figure, especially when it comes to achieving milestones. However, I have to commend my entire family, particularly my mum, for stepping up and ensuring that I never felt like I missed out on anything. While there will always be a part of me that is missing, I am grateful for their support and love."

"I hope that somehow, he knows I'm trying to make him proud."

On his 21st birthday, Robert honored his father.

"It can be heartbreaking. I can’t beat around the bush. It’s really hard, particularly when it’s those milestones. It’s difficult navigating that without a father figure." — Robert Irwin, Stellar magazine

"On my 21st birthday, I found pictures of my dad celebrating his own 21st. Although it can be challenging to celebrate milestones when someone is absent, I will keep my dad's memory and passion with me as I embark on this new chapter of life. I am grateful to have such an amazing family to celebrate with me today. Let's raise a glass!"

Bindi Irwin, the older sister, remarked, "Dad is incredibly proud of you."

Steve, famously known as "The Crocodile Hunter," died in 2006 at the age of 54 after being stung by a stingray while filming in the Great Barrier Reef for the documentary series "Ocean's Deadliest." At the time of his death, his son Robert was 2 years old and daughter Bindi was 8. Steve and his wife, Terri, were married for 14 years before his death.

In the wake of his father's passing, Robert has continued Steve's legacy in numerous ways.

""Dad instilled in me a passion for being there for my sister and myself, as he was a devoted dad who was present in my early years, even though he passed away when I was young. This passion and zest for life have become my foundation," he said in a 2022 interview with People magazine."

In that year, Robert published a book titled "Robert Irwin's Australia," which was a tribute to his father's passion for photography.

"Robert shared with People that his dad was a highly passionate photographer who was equally enthusiastic both behind and in front of the camera. Photography has always been a part of his life."

Robert had been working on the book for years before its release, but the idea had always been simmering in the background.

He said, "I thought, 'I want to honor my father's legacy by creating something that truly reflects my unique way of carrying on his traditions.'"

One year ago, Robert and Bindi paid tribute to their deceased father on Steve Irwin Day.

"Robert shared a throwback photo of himself and his daughter Bindi with their dad, captioning it with a reflection on his father's impact on the planet and the inspiration he provided to a generation. He also expressed his gratitude for the memories he has of his dad through family stories and captured moments."

The wildlife photographer stated that although he misses him dearly, it is significant to him and his family that they can commemorate his values annually through a special day.

Robert has since starred in various television shows throughout his career, including "Crikey! It’s the Irwins." However, these days he's embracing his next big move.

In 2023, it was announced that Irwin would replace Dr. Chris Brown as the co-host of "I'm a Celebrity...Get Me Out of Here!" alongside returning host Julia Morris. The show's 10th season premiered this year.

"Robert told Stellar that live TV gives him the biggest adrenaline rush ever, which he loves."

Prince Harry's resemblance to him has been noted by fans since his live TV debut and photo shoot with Stellar.

Robert Irwin is the modern-day Prince Harry, and I don't need to elaborate on that further.

"Robert Irwin is gen z's Prince Harry," another wrote.

Robert expressed excitement about his new appearance and career direction, stating that he hopes to make his father proud while embracing the future.

"Stellar was told by him that life involves pushing oneself and having fun. He shared that he has learned a lot and wants to continue his family's legacy, but in his unique way."

"Although my heart still beats khaki, stepping out and trying something new occasionally is very important to me," he said.