The rise of KSI, the 25-year-old millionaire who's fighting Logan Paul after inventing YouTube boxing matches

KSI was born in London, after his parents moved to the UK from Nigeria. "They would work their asses off," he told The Sun in an interview.

He eventually moved with his parents out to the suburbs of Watford and went to a fee-paying school. It would now cost you £20,000 ($26,000) a year to send your child to the "posh" Berkhamsted School.

Despite the expensive education, KSI said he discovered YouTube from the age of about 15 and ended up failing his A-Levels. "Back then, people would be like: 'What are you doing? You're such a weirdo. Why are you making videos online?'" he told the Sun.

He created his first YouTube channel in his early teens, the now-defunct "JideJunior." Almost all the videos feature KSI playing "FIFA 08," a theme that would continue in his main YouTube channel.

Eventually, JJ would adopt the name "KSI", which stands for "Knowledge, Strength, Integrity."

In 2010, KSI created his main channel and began posting game play footage from "FIFA 11." He began to amass a big following, and after just two years in he made enough money from YouTube ads and sponsorship to drop out of school.

KSI teamed up with six other YouTube gamers to form a group of creators called The Sidemen. "A sideman is basically someone's bitch who just follows them around," said fellow Sidemen member Miniminter in an FAQ. "I was basically JJ's [KSI's] bitch that followed him around."

The Sidemen brand and channel mostly revolved around the YouTubers playing video games and charity football matches with each other.

The Sidemen would go on to live together in various plush houses in London. Their latest is a mansion at an undisclosed location in South London. It's thought that's where KSI lives.

Out of all the Sidemen members, KSI has the biggest following with 18 million subscribers.

He's a young millionaire, with estimated annual earnings of up to £2.3 million, according to SocialBlade. Asked about his wealth by TV presenter Piers Morgan, he said: "I'm doing alright."

KSI has branched out into music, posting "diss" tracks insulting other YouTubers - including his fellow Sidemen. The drama keeps viewers hooked.

KSI's younger brother is also on YouTube, posting under the name ComedyShortsGamer. The two often cross over into each other's channels.

KSI has had some controversy. He was banned from the Eurogamer event and sponsor Microsoft dropped ties with him last year after he made sexist remarks to attendees. He subsequently apologised.

KSI is about to become even richer after he pioneered a new genre of crossover: The YouTube boxing match. His first fight was against Joe Weller, a YouTube creator on the same talent network.

The YouTube boxing match involves two famous personalities fighting each other just like a real match. KSI fought Weller in London's Copper Box Arena in 2017 and won the fight.

Here's the full fight:

He'll be taking on a much more popular and controversial YouTuber, Logan Paul, in August 2018 at the 20,000 capacity Manchester Arena. The event is expected to net the pair millions.

They whipped up anticipation for the fight in a bad-tempered press conference in London, in which KSI hurled insults at Paul's girlfriend and family.

KSI said he's successful because he creates new trends. "When it came to diss tracks I found my way into that," he told Esquire. "Now with boxing, I’ve created a new trend. I’ve always adapted well, and that’s what’s led to my success."