Mr Higgins was left in a pool of blood with a broken cheekbone and shoulder, while the four offenders walked off towards Albert St.
David Higgins, boss of boxing promoting company Duco, confirmed he and his brother were involved.
"As far as I'm concerned it's resolved. I'm a forgiving person, I move on with my life."
Andrew Higgins declined to comment, saying: "I'd prefer to leave it as a private matter."
Duco has put on numerous high-profile events including Shane Cameron's bout with Monte Barrett, Joseph Parker's fight with Francois Botha, as well as speaking events hosted by the likes of Gordon Ramsay, Andre Agassi and Al Gore.
The army confirmed that the Jackson brothers were serving soldiers.
A spokesman said they would face an internal investigation to decide their future with the military. Their discharge would be considered as part of the review.
At the Auckland District Court hearing on Monday Judge Russell Collins said the matter had started off in a "more serious vein" but the police had reduced the charge.
He said the police case did not show that the two Jackson brothers used any force against the victim.
The brothers' lawyer, Steve Cullen, told the court his clients had made the "pragmatic decision" to plead guilty as parties, because they wanted to move on with their lives.
Judge Collins said it was also unclear what the roles of the other defendants were, and while one of the men admitted punching the victim in the body, he did not admit to any punches to the head.
He said the matter had been before the court for 18 months and could not be remanded again.
All four had attended a restorative justice conference with the victim. who had forgiven them. They had also paid $250 each towards the man's medical costs.
Judge Collins said all four men also had "glowing references" and none had previous convictions.
