NEW YORK — The distance between the hometowns of Gennady Golovkin and Daniel Jacobs is vast, with some 5,870 miles, including an ocean, stretching between Karaganda, Kazakhstan, and the Brownsville section of Brooklyn. But on Saturday night, the two will be separated by no more than 20 feet of canvas in a boxing ring.

And considering the kind of fight it is expected to be, the two are likely to spend most of their time a lot closer than that.

Which is appropriate, because in spite of their obvious differences in ethnicity, background and fighting style, Jacobs and Golovkin, who will meet to unify the middleweight title at Madison Square Garden, have more in common than one might expect.

Both were raised in environments in which toughness was not just a virtue, but also a requirement. Somehow, both of them, through upbringing, sheer force of will or merely good sense were able to avoid falling into the spiral of failure their neighborhoods offered as a virtual birthright.

Both were schooled in the art of toughness by older brothers who recognized the necessity of a hard outer shell. Both have faced, and overcome, intense personal setbacks.

And for both of them, everything they have achieved so far will not mean all that much without a victory Saturday night.

Golovkin, 34, is widely considered one of the world’s best all-around fighters and is as intimidating to middleweights as Mike Tyson was to heavyweights 30 years ago. For him, Jacobs, 30, is the last obstacle that stands in the way of a megamillion-dollar showdown with Saul “Canelo” Álvarez, the fight that Golovkin’s people believe will catapult him to crossover stardom.

And for Jacobs, who beat a potentially deadly form of bone cancer that wrapped around his spine, and then came back to win a world championship, a victory over Golovkin, known as Triple G to fight fans and simply as G to his intimates, would elevate his personal story from an inspiring footnote in boxing history to the kind of tale they make movies about.

How competitive a fight Golovkin-Jacobs turns out to be remains to be seen — Golovkin is, after all, a 7-1 favorite with three of the four world middleweight titles — but on paper, at least, it is a matchup of real drama. One fighter (Golovkin) specializes in not just beating his opponents, but breaking them; the other fighter (Jacobs) is informed and emboldened by his struggles and claims that “now I know that I can’t be broken.”

Jacobs believes the titanium rods in his spine are symbolic of the steel in his backbone, all of it stemming from an 18-month ordeal that had doctors doubting he would ever walk again, let alone fight. But ultimately he was fighting and winning again, and just over three years after his diagnosis, he won the vacant World Boxing Association middleweight title in 2014 with a fifth-round knockout of Jarrod Fletcher.

“To beat a guy like Golovkin, you have to be mentally tough,” said Jacobs, whose nickname is the Miracle Man. “And what guy could be tougher than me, after what I’ve battled?”

Hard upbringings

The Brownsville section of Brooklyn has spawned an unusual variety of public figures, good and bad. It was the birthplace of the gangsters Mickey Cohen and Henry Hill, and it is where Murder Inc. had its roots. It is also where the Rev. Al Sharpton was born as well as New York Yankees great Willie Randolph, who went on to manage the New York Mets.

Brownsville is also where an inordinate number of prominent professional boxers grew up, including Tyson, Riddick Bowe, Zab Judah, Shannon Briggs and now, Jacobs. During their formative years, Brownsville was the kind of place politicians used as shorthand for crime-ridden urban decay. To this day, it remains one of the parts of Brooklyn that has not been reinvented.

And it was in this challenging environment that Jacobs, a self-described “mama’s boy,” was raised by two women — his mother, Yvette Jacobs, and his grandmother, Cordelia Jacobs — after his father left the family when he was 3.

“I don’t want to say it was a war zone,” Jacobs said of his neighborhood. “But I guess that’s what it was.”

Jacobs’ introduction to fighting came at the hands of his older brother David, who amused himself by using Daniel as an occasional punching bag. “I didn’t need to go fight in the streets because I had it in within my household in a sense,” Jacobs said. “He was more of the rough kid than I was. He was the one who brought the toughness out in me, I guess.”

And his introduction to boxing came courtesy of a neighborhood bully who bested him in a street fight. When Jacobs learned the bully was training at a Police Athletic League gym a couple of blocks from the apartment building in which he grew up, he went to the gym seeking a rematch in the ring with gloves on.

“Within two weeks, we sparred, and I actually beat the kid up,” Jacobs said. “After that, I never saw him in the gym again. I stuck with it. For me, it was love at first sight. It was like nothing I ever experienced before. The grittiness of it, the smells, people working hard, it was definitely an environment I knew I could stick with.”

Golovkin is the son of a coal-miner father and a mother who has both Kazakh and Korean heritage. He had a similar experience in Karaganda, a place in interior Kazakhstan that, in the Soviet era, was used as a punch line.

During Stalin’s time, released prisoners and other perceived enemies of the state were sent to work in its mines. Golovkin’s adult brothers Sergei and Vadim took him to a boxing gym when he was 10 and delighted in not only the natural skill he displayed, but also his obvious relish for the sheer combat the sport required.

It was there that a young Golovkin discovered that his brutal, high-pressure boxing style could be his ticket out of Kazakhstan. In the same way that aspiring major league ballplayers from the Dominican Republic are known to swing aggressively — “You can’t walk off the island,” goes the adage — so, too, did Golovkin come to understand he could not box his way out of Central Asia.

“From the beginning, I was more interested in a traditional fight, a true fight,” he said. “Not just box. Destroy my opposition. In Kazakhstan, you need something to set you apart.”

He got a bloody nose his first day in the gym and found it neither repelled nor deterred him. “I thought, OK, this is different. This is not like soccer or basketball. Not a game.”

And he found he thrived at it, the nastier the better. “Boxing should not be like pingpong,” he said. “No bing, bing, bing.”

Twenty-five years later, Golovkin — who has never been knocked off his feet as an amateur or a professional — says that bloody nose was the last time he can recall being hurt by a punch.

He also acknowledged that his brothers often went out of their way to match him against bigger and older boys, as a test of not only his prowess, but also his manhood.

“That is the way you grew up in Kazakhstan,” he said. “It wasn’t bad. It was just life. Real life.”

Now, Golovkin is one of the world’s best-known Kazakhstanis, and more than 500 of his countrymen are expected to travel to the fight. Because of the 10-hour time difference, the fight will start at about 9 a.m. Sunday in Karaganda, and it is expected no one will be sleeping in.

Both of Golovkin’s older brothers died fighting in the army. The family was never given the full details of their deaths — Golovkin does not even know where they were fighting, or specifically against whom — and it is a subject he prefers not to dig into too deeply. But their memory lives on in his son, named after the younger of his two brothers, and in his other brother’s son, Evgeny, now 30, who is a permanent part of Golovkin’s entourage.

As is Golovkin’s fraternal twin, Maxim. Both were standout amateur boxers in Kazakhstan, both middleweights, and according to Golovkin at least, Maxim might have been the better of the two.

But because Gennady was born 15 minutes before Maxim, when it came time to turn pro, it was decided that the older brother would do so while the younger one would remain behind, tending to their parents.

“From what I’m told, this guy was technically better,” said Abel Sanchez, Golovkin’s trainer, in reference to Maxim. “But this guy wanted it more.”

“That door opened for me, and I go through it,” Golovkin said. “Just like that. That’s my life.”

“Within two weeks, we sparred, and I actually beat the kid up. After that, I never saw him in the gym again. I stuck with it. For me, it was love at first sight. It was like nothing I ever experienced before. The grittiness of it, the smells, people working hard, it was definitely an environment I knew I could stick with.”— Daniel Jacobs