The brothers can't give enough credit for their success to their father's work ethic.
"I looked up to him in every way and listened to every story he told me about life and fighting," Nick wrote in a profile posted on the USMTA website. "My dad worked his butt off at every aspect, as a fighter, trainer, father, and husband . . . We knew that we were not going to be handed anything for free. We were going to have to earn everything through hard work."
Despite the intense workouts, John says, he never expected his sons to end up as professional combat fighters.
"Everything's going gangbusters," he says, gleaming with pride over Nick's recent bout in Vegas and a fight in China with Damien on the card. "Who would have known?"
Bob Karmel, a Thailand-trained fighter, had a pretty good idea about the brothers' potential.
They call him Master Bob, a title he earned after three decades as a fighter, instructor, and one of the first Americans to fight and train fighters in Thailand.
The website www.tigermuaythai.com describes the sport's eight points of contact as mimicking ancient weapons of war.
"Hands become the sword and dagger, shins and forearms [are] hardened in training to act as armor against blows, and the elbow [is used] to fell opponents like a heavy mace or hammer, the legs and knees [are] the ax and staff. The body [operates] as one unit. The knees and elbows [search] constantly, and [the fighter tests] for an opening while grappling and trying to spin an enemy to the ground for the kill."
Trying to hone the all-but-deadly skills in his fighters is what Karmel does. And he does it well, although it racks his nerves on fight nights.
"The day of the fight, come noon, don't talk to me," he says. "I'm nervous. I can't eat. Once we get into the ring, I second-guess myself. Did I do everything I could have done [to train the fighters]?"
He met the brothers at Lion's Den, a Scottsdale gym where he led a Muay Thai program for three years. While there, he produced eight national Muay Thai Champions and brought home the National Team Championship at the 2010 Thai Boxing Association's annual Muay Thai tournament in Iowa.
Lion's Den since has closed, but Karmel opened his own gym: Best Muay Thai in Tempe. He works with Valley promoters Bounded Fist and Bad Blood to organize fights, and he manages some fighters.
"There's a lot that goes on with the sport beyond the fighting," he says, recalling many days and nights of traveling across the country to events, everyone piled in one car, stuffed in the same hotel room, spending weeks trying to get his fighters on various cards. "It's just nonstop. And then there's trying to keep them out of trouble. These boys are no angels."
Nick doesn't deny this.
He tangled with the cops when he was a teenager, getting busted for underage drinking, speeding, and disorderly conduct.
"Given the neighborhood I grew up in, I could easily be locked up now," he says. "I was in trouble growing up, but I never abused my fighting skills; it was just rebellious teen stuff."
He says Karmel built him and his brother into the ring competitors they are today.
"It's been a rough road through my years," Nick says. "Master Bob molded me and my brother into unstoppable forces. We've only begun to scratch the surface."
Experts agree that pro Muay Thai fighters Schilling, Ross, and Adanaz are at the top of the sport in the United States — for now.
Fox tells New Times that Buakaw is Thailand's top fighter.
"For Canada, it would be Simon Marcus. For Russia, it would be Levon Artem. And we must not forget the females like Valentina Shevchenko from Peru and Caley Reece from Australia," Fox says. The matches between female fighters are just as potent as the male contenders.'
Each holds various world titles in bouts sanctioned by the World Muaythai Council, the sport's official world governing body, established by the Thai government. They'll be fighting on June 14 in Monaco to defend their titles. Yet several other bodies govern Muay Thai fights and offer contenders titles and championships in the disorganized sport.
"Think about it like high school," Karmel says. "Nick and Damien are the freshmen among U.S. contenders. The older guys are just a generation or so ahead of Nick and Damien."
He predicts that the brothers, who have been on the undercard when fighters like Schilling and Ross are the main event, will take many titles from them in the long run.