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There's a moment in a fighter's life when he knows he's got it. When, after being knocked down hundreds, even thousands of times, suddenly he's the wrecking ball and not the crumbling building. When he bests someone in the gym he once looked up at with stars in his eyes.

It's just not usually a 17-year-old girl.

Of course, Stephen "Wonderboy" Thompson's nemesis was no ordinary teenage girl. When others were playing tennis, his sister, Lindsay, was at the dojo. When other kids whiled away the time with video games and nonsense, she was at the dojo. When friends were at the mall? You guessed it. She was at the dojo.

In the Thompson family, martial arts was not just an activity that put food on the table. Ray Thompson's Upstate Karate was also a sanctuary and, at times, almost a prison. Training was compulsory, and it was hard.

"I knew all the benefits I had derived from martial arts instruction and training, and I wanted my kids to experience that as well," Ray Thompson said. "We put the same emphasis on the martial arts that we did on school. It was not an option."

Ray had begun his martial arts journey at 18, inspired by Elvis Presley of all people.

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"I thought Elvis was really cool," Ray said. "A good singer. A good dancer. A handsome fella who wooed the ladies. And he did those cool karate moves.

"Well, I knew I couldn't sing, and I knew I couldn't dance. And I didn't have those Elvis Presley looks. But I thought, maybe, I could do some of that karate stuff he did."

It may have have been a light-hearted beginning to his life's work, but years fighting on the international circuit as the Master of Disaster soon convinced Ray that martial arts were a serious business. It was a lesson he passed on to his family and students.

When they were barely toddlers, each of Thompson's five children started attending classes with their dad. Only when they were 16, he figured, were they old enough to decide whether or not they wanted to continue.

"I remember being three years old, my dad would be dust-mopping the mat, and I'd be piggy back," Lindsay said. "We just grew up in it. There are football families, baseball families, basketball families. We're a karate family. We're a martial arts family. That's what we did. If we even hinted at wanting to do something else, it was like 'Nope.' This is it. This is what you're focusing on, and you're going to be great at it."

Credit: Lindsay Thompson Machado

Lessons didn't end at the dojo doors. When brother and sister squabbled, a pretty typical sound in most families, their father moved the coffee table out of the way and had them settle their beef in the middle of the living room. No closed fists were allowed, to prevent cuts. Anything else was fair game.

"My dad said 'you guys want to fight? Alright. You gonna fight,'" Lindsay said. "And he was like 'Go. You stop and you'll get it from me.' We'd be beating the s--t out of each other. Excuse my French. Until we were crying and we didn't want to hit each other anymore. Only martial arts families can get away with stuff like that. Today my parents would be in jail. We didn't fight anymore after that. At least not around dad."

The result of all that tough love and martial discipline, in Lindsay's case, was a young fighter with exceptional power and skill. And a young lady in desperate need of a sparring partner.

"I had stuck with it for 10 years. Most people quit," Lindsay said. "They don't stick with it long enough to get good at it. But my brothers had to be there, so my dad was constantly saying, 'Stephen, get in there.' He was the closest thing there was to a training partner that could push me."

Stephen (11-1, 6 KO), who fights Johny Hendricks Saturday on Fox Sports 1 in a bout that might well determine the next UFC welterweight contender, isn't too proud to relay the results of those sparring matches.

"She kicked my butt," he said with a laugh, something his father confirmed.

"She was a couple of years older than Stephen, and she was a pretty stout young lady," Ray said. "She was the first of my kids to fight in an authentic kickboxing match. I put her up against a female national champion. And my daughter ended up winning that match.

Credit: Lindsay Thompson Machado

"Stephen really looked up to his sister. For a number of years, she was larger and definitely stronger than Stephen. So Stephen took some abuse for a while. She was a tough young lady and a good fighter. It had a hardening effect on him. You hammer that nail long enough, and it gets hard. When he was around 14 or 15 years old, Stephen started coming into his own. And he came to a realization that he could do this."

"The ass-kickings stopped," Lindsay said. "I remember vividly, and it happened overnight, a switch flipped in him. He just got it. Something happened, and it clicked with him. He was a beast, and I remember leaving training crying because he was kicking my ass now. And then I was like 'hey, let's hang out. We can be friends. I'm the nice sister.'"

For Stephen, it was as if he'd seen the future. Beating his sister gave him the confidence to continue on his own path and to attempt to follow in her footsteps and actually compete in the ring. No giant gloves and padded helmets. An honest-to-goodness fight.

"I was training with her and doing fairly well, after years of getting my butt kicked. I thought 'why not step out there and fight?' You were supposed to be 16, but it was three days before my birthday," Stephen said. "My dad threw me to the dogs. He set me up with a guy who was undefeated and 26 years old. But I ended up beating the crap out of him.

"I did it with ease and felt great out there. My dad knew my potential. I didn't see it until afterwards. After that fight, I realized 'I can do this.' That's what he wanted to show me. He put me out there with one of the best in my first fight. He was trying to show me I could do a whole lot better than I thought was possible. And that's when I got my nickname."

Ray picks up the story from there, one that has become part of family lore.

"After the fight, his opponent was being interviewed in the ring and said 'I wonder why I got in the ring with that boy.' And the announcer called Stephen 'the Wonder Boy.'"

Credit: Lindsay Thompson Machado

Thompson's kickboxing exploits read like a work of fiction. He won titles everywhere he competed, from South Carolina to Szeged, Hungary. Only a devastating knee injury suffered against current Glory Kickboxing star Raymond Daniels slowed him down.

"When I tore the ligaments in my knee, doctors told me I'd never fight again," Thompson said. "They said I'd never be the same. When I heard that, it about broke me. Because this is my dream. It's what I love to do. I was still young, and I remember riding home with my dad and him saying 'discard what that doctor said to you. You can keep fighting. I'm going to help you get there.'

"The next day I was at the gym, sitting in a chair with my leg propped up and hitting a bag. The next day. I wasn't going to let it get me down. I kept going. And I've had three surgeries since, one actually right after my fight with Jake Ellenberger. But my knee feels great. It's a mental thing. After suffering one of these injuries, you can do more than you think. If you're strong mentally, you can do anything."

As great as he was in the kickboxing ring, his future was always in the UFC. His father had taken him to see UFC 3 in Charlotte when he was 12 years old. The Octagon, from that moment, was perhaps an inevitability.

Although known for their stand-up prowess, there was nothing myopic about the Thompson's approach to the martial arts. They studied a number of disciplines and former jiu-jitsu legend Carlos Machado, who married Lindsay in 2001, began doing seminars at Upstate Karate years before it was trendy in karate circles to rediscover their sport's grappling elements.

Credit: Lindsay Thompson Machado

"My dad had us cross-training at a very young age," Lindsay said. "Stephen was like nine when he was first introduced to Brazilian jiu-jitsu. We're very lucky that my dad was one of those 'karate guys' who was very open-minded and saw the value in cross-training.

"It's not like one way is the only way. Not in our family. Everything complements. Its doesn't contradict. When you look at it like that you can learn for life. You'll never get bored."

To prepare for a career in the Octagon, Thompson sought out the best in the world. A longtime sparring partner of former welterweight champion Georges St-Pierre, Stephen now trains regularly with middleweight standout Chris Weidman, whose younger sister is engaged to Thompson's brother, Tony.

Combined with his father's expertise in the stand-up game and the time-tested efficiency of Machado jiu-jitsu, Thompson has all the tools to challenge for UFC gold. And that, more than money, was always the plan.

"We started in the fight game not necessarily to make a living at it. We did it for the glory," Ray said. "He wanted to get out there and test his skills and make a name, maybe even go down in the history books. Those are the reasons that will make a fighter train hard and go beyond where they'd take it if it was just a job. The fact he makes a living doing it? That's just icing on the cake."

"Here I am," Thompson said. "Fighting the No. 2 guy in the division and maybe after that, fighting for a title. I'm on that path. And it's so surreal, man. It really is. I'm going to give it my all to get that title. And whether I make it or not, I'll know I've competed with the best. And that's enough for me."

Jonathan Snowden covers combat sports for Bleacher Report.