KSI won the battle of the YouTube stars as he defeated Logan Paul by split decision on Saturday night.
But the bout wasn't without controversy.
Paul was docked two points after punching KSI on the floor in the fourth round.
That proved to be pivotal. Paul actually would have won the fight if he wasn't docked those points.
Paul had a number of big names watching him ringside, including younger brother Jake.
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Jake, who is also a YouTuber, spoke to the media after the bout and he was not happy at all with the decision.
Jake beat KSI's brother in the ring last year and has now claimed that the sport is 'rigged'.
"With that decision, that's just b*******," he said.
"At the end of the day, I've been in this sport for a year now and, I probably shouldn't be saying this, but all this s*** is f****** rigged.
"You see people wining and dining each other, people at the Staples Center. Who was at the Staples Center last night with KSI? Joe Markowski.
"This sport is rigged, that's for sure.
"The short amount of time I've been here, I've heard multiple stories about people paying stuff off, choosing fights, what time people sign contracts.
"It's not an excuse, I'm just saying."
Jake then took to Twitter to complain some more.
"I don't and many people don't agree with the decision that was made... It is what it is..." he wrote.
"I've received dozens of texts saying they have NEVER seen two points taken away from a fighter since Mike Tyson bit the dudes ear off... ABSURD!
"My brother won that fight and is clearly a better boxer. KSI was saved with the decision the referee made...
"Over a minute to recover in the corner after being knocked down? Insane...
"I haven't been in this sport for long but can tell you it's not everything we think it is...
"Lots of money and pushed DOLLAR SIGN narratives we don't know about. RIGGING."
Jake clearly hasn't taken his brother's loss very well at all.News Now - Sport News