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For years, the two best heavyweights on the planet have been brothers Wladimir and Vitali Klitschko.

Their stranglehold on the division has been absolute, with nobody coming close to touching them as they decimated one contender after another to keep all of the belts in the family.

Since Wladimir won a world title for the second time in 2006, he and Vitali (who reclaimed a title in 2008 after a nearly four-year retirement) have combined to make 24 defenses, winning every single one of them in dominant fashion.

They said for years that their goal was to simultaneously hold heavyweight titles, and they accomplished that and more, becoming a two-headed heavyweight monster, collecting all four alphabet titles and ruling the division together until just last week when Vitali, deeply involved in Ukrainian politics, vacated his belt.

But for all those years, as great as the Klitschkos were -- and make no mistake, they’re among the greatest heavyweights in boxing history -- the question of who truly was No. 1 was never answered, nor will it be.

Typically, it reaches a point where the top two fighters in a division eventually face each other. There is public pressure, a chance for greater glory and big money. Throughout their careers, the Klitschkos were routinely asked about fighting each other. They nicely answered countless times: They’re best friends and promised their mother they’d never fight each other.

Therefore, the world would have to live with two heavyweight champions, as a unification match was out of the question, no matter how big it would be and how many tens of millions of dollars it would generate. Tearing apart a family for the sake of a prizefight was not worth it to them.

After all, this is not tennis, where sisters Venus and Serena Williams have played many times, including in the sport’s biggest tournaments. Tennis is a game, but you don’t play boxing. These giant men hitting each other in the head is serious, damaging business, and they would have none of that.

It’s not like they’ve never been in the ring with each other, however. They spent years sparring. As the brothers have recounted to me over the years, those sessions were intense and brutal. They love each other, but they’re competitors, and when they sparred, they took it seriously.

“We used to spar before and I tell you we were so competitive,” Wladimir told me a couple of years ago. “No one wants to give up, and it was ending bloody for both of us. It’s very emotional and there is, of course, a healthy competition between us.”

But it got to a point where it became so rough and violent that their mother pleaded with them to stop and, just like that, they never sparred again. They always worked in each other’s corner on fight night, but they would never again stand across the ring from each other.

But boy, oh boy, what if they did fight?

If emotions ran so high just in those legendary sparring sessions, they would surely boil over in a real fight, right? The Klitschkos are proud men and would be out to win, so I think it would be a classic heavyweight brawl until the end.

Wladimir is quicker, has better footwork and is a smoother boxer. He is also the better puncher. But Vitali would have a slight size advantage, has a much better chin (never down in his pro or amateur career) and has the mental edge as the older brother.

It wasn’t easy, but once, a couple of years ago, I convinced the brothers to break down their hypothetical fight.

“If it’s going to happen, it will be a bloody mess. It’ll be bad,” Wladimir said. “But I won’t fight my brother, even in my dreams.”

Said Vitali, “If you compare the styles, Wladimir is the much smarter fighter. I am the street fighter. I just go in the fight and try to knock him out. If brothers fight each other I think we can easily put 100,000 in the stadium.”

Alas, it will never happen.