Benn (left) and Eubank Jr (right) will meet at a catchweight of 156 poundsConor Benn and Chris Eubank Jr will fight at London's O2 Arena on Saturday, 8 October, almost 30 years since their fathers shared one of the most iconic rivalries in British boxing history.
The bout will have a catchweight limit as each fight at different weights.
Eubank Jr, 32, joined the professional ranks in 2011 and has recorded 32 wins and two defeats.
Benn, 25, has won all 21 bouts since turning professional in 2016, with 14 knockouts.
A rivalry rekindled
Chris Eubank Sr (left) and Nigel Benn were bitter rivals in the 1990s, fighting twice in the United KingdomThe announcement rekindles the Benn-Eubank family feud.
Their fathers - both former super-middleweight world champions - fought twice, with Eubank Sr winning the first fight in 1990. The second, three years later, ended in a split decision draw.
The bitter rivalry earned both men household name status, with the seemingly authentic bad blood between them generating huge interest.
Their rematch was aired on terrestrial television in the United Kingdom and watched by 15.6 million people.
'A fight for the legacy' - what they said
"He has walked the same path as I have. I know his struggle. Living in the shadow of a legend and trying to break out of that shadow and make his own name," said Eubank Jr.
"In terms of anticipation, legacy and hype, it's the biggest fight of my career."
Benn is also keenly aware of the family history. "This fight is for the legacy and was an opportunity I felt I couldn't pass up," he said.
"My team and I had other options on the table as I'm currently ranked top five with all governing bodies at welterweight and no doubt I'm looking for a world championship fight very soon, but this fight is embedded with so much history and I know it's one the public really want to see.
"To me this fight is personal - it's more than titles and rankings, this is unfinished business between our families!"
"I can't quite believe this is happening," Benn's promoter Eddie Hearn said. "Ever since they both turned professional, people talked about this moment."
Catchweight stipulations
Eubank Jr - who beat Welshman Liam Williams (right) in February - has suffered losses to fellow Britons Billy Joe Saunders and George GrovesEver since Eubank Jr and Benn each turned professional, it was widely believed the clear weight difference between them may prevent the fight from taking place.
In February, Eubank Jr played down the chances of a showdown with Benn, saying it could possibly take place in "a couple of years". Just a few weeks ago Benn's promoter, Eddie Hearn, also distanced himself from the fight, saying they were pursuing American fighter Keith Thurman.
Benn boxes at welterweight (147lbs) while Eubank Jr has operated at both middleweight (160lbs) and super-middleweight (168lbs).
The catchweight limit will see the pair having to make some adjustments to their natural fighting weight. They will weigh in on Friday, 7 October, the day before the fight.
It is understood a rehydration clause may be included in the contract, with a subsequent weight check on the morning of the fight, meaning there is a limit to how much weight each fighter can gain on fight night, exceeding which will risk facing financial penalties.
Benn was last in action in April, stopping Chris van Heerden in the second round'Tapping into their fathers' legacy' - analysis
BBC Sport's boxing reporter Kal Sajad
It all seems a little surreal.
Up until a few weeks ago, when the rumours first started to circulate, the idea of a Eubank Jr v Benn clash was just pure fantasy.
Eubank Sr and Benn Sr were not just bitter rivals but legends who transcended the sport. After their first fight, a victorious Eubank Sr told the interviewer he was "in too much pain to talk". The two men went to war. Twice. Their sons will have a lot to live up to.
Both boxers have created a fanbase in their own right, but are also tapping into the legacy and support of their legendary fathers; it is a fight which makes sense and has all the potential to pull in the casual sports fans.
Some may feel the build-up to their Eubank Jr-Benn may become a little forced or orchestrated at times, but they are far from camera shy or wary of speaking their minds.
Inside the ring, you see a match-up between two talented fighters. Eubank Jr will treat you to flashy combinations and hand speed, and he has the ability to finish off an opponent with a flurry of punches. Benn fights with real intensity, possesses that one-punch knockout power and is one of the most improved British fighters in the sport.
Eubank Jr, with his weight advantage and experience, will be the favourite. But the pressure is on - many feel he has underachieved as a professional. For Benn, he has everything to gain. Beating the 'bigger man' would catapult his career to incredible heights.
