Kostya Tszyu has congratulated son Tim after he replicated his famous dad by becoming a boxing world champion.

Tim produced a dominant performance in Sydney on Sunday to defeat Tony Harrison via TKO to claim the interim WBO super welterweight title.

It may just be an interim title, but it means Tim and Kostya have joined an exclusive group of just six father-son boxing world champions.

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The referee stopped the fight in the ninth round after a flurry of uppercuts left Harrison dazed, sparking jubilant scenes.

As the roof nearly blew off Qudos Bank Arena and confetti went everywhere — Tszyu was immediately mobbed by his trainer and uncle Igor Golubev, grandfather Boris and younger brother Nikita, who won his fifth pro fight earlier.

Tim was also embraced by his long-term partner Alexandra Constantine, but one member of the family was missing.

Kostya, a former light welterweight champion, now lives in Russia where he has started a new family after leaving his old one behind.

Kostya had been set to attend Tim’s fight against undisputed super welterweight champion Jermell Charlo in Las Vegas in January before it was postponed, but he stayed in Russia for this fight to look after his young daughter, who was sick.

The 53-year-old surprised Tim by flying in to watch his professional debut in 2016, but he hasn’t been ringside for his son’s fights since.

Tim didn’t enjoy his dad barking instructions at him from the other side of the ropes, and Kostya now tunes in to watch his fights via FaceTime.

And it was no different on Sunday — Tim’s management No Limit shared a photo of Kostya watching his son drape the champion’s belt over his shoulder on a family member’s phone.

Kostya also posted a video message on Instagram, in which he congratulated his sons Tim and Nikita on their respective victories, speaking in Russian.

“The fight has just ended,” he said, smiling with the fight on the TV in the background.

“Today Timothy became the world champion. Congratulations, son. Of course there were mistakes but you did well.

“And also Nikita. You need to study. I love you. Well done. Congratulations.”

It was a heartwarming message, which Tim shared on social media, but it was hard not to notice the backhanded compliment that his eldest son made some “mistakes”.

Tim has constantly been derided by rivals who believe he is riding off the coat tails of his famous dad, but he made the world sit up and take notice against Harrison.

The knockout win saw him win a world title, earn a shot at Charlo and arguably most importantly, take a step out of his father’s shadow.

Tim recently gave an insight into the heartbreaking family split after Kostya moved to Russia once his boxing career was over.

“It was tough because you always think your parents, it’s like a fairytale, they love each other,” Tim told the Howie Games podcast.

“Then all of a sudden it’s completely gone. Dad moved to the other side of the world. For me, it wasn’t a big shock because he’d always be in and out. As soon as he finished boxing in 2005, he was always in out and of Russia non stop.

“When dad left after his career, it sort of changed everything because he was extreme and then it sort of gave us freedom to explore.”

Growing up with a world champion for a dad wasn’t always easy and Tim said at the peak of Kostya’s career, he had to deal with an absent father.

“I remember my dream was always to have … every year at school there was a father’s day camp. I never had one father’s day camp. Never had a father’s day breakfast.

“He was never there for us. Now looking back to it, I understand where he came from because to get to where he got to, there’s a lot of sacrifice.”

Unsurprisingly, Charlo said he wasn’t overly impressed by Tszyu’s performance and welcomed a blockbuster world title bout against the Australian, who is aiming to become just the ninth undisputed world champion in boxing history.

The brash American said his hand should be good to go towards the end of the US summer, while there is already talk Team Tszyu are keen on a fight in Vegas in July.

Despite his absence, it’s obvious Tim still idolises Kostya, and the sight of the son of a gun taking Charlo’s belts off him with his legendary dad watching on ringside would be a sight all Australian boxing fans hope eventuates.