Their attack was only broken up when a lone police officer charged in to stop them, and a member of the public tripped one of the defendants as they ran away.
The pair took part in a four-on-one beating, where a witness described seeing 'penalty-like kicks' that snapped the victim's head back 'like whiplash in a car accident'.
John Butterfield QC, in sentencing, said: "I want to commend the bravery of the police officer and the member of the public on that night. They show some of the better qualities of humanity that these two do not exhibit."
Billy Holland, 20, and his cousin Kieran Holland, 20, both from Kettering, were sentenced in Northampton Crown Court yesterday (April 21) for causing grievous bodily harm. Kieran, who the court heard started the attack with a punch to the head, was sentenced for causing grievous bodily harm with intent.
They were on a night out in Kettering town centre in July 2014 when a disagreement with another man turned violent.
Mr Butterfield said: "I imagine this was some disagreement that started in a nightclub and was resolved outside on the pavement.
'Kieran Holland punched the victim to the ground before all four of the group 'put the boot in' with stamping and kicking. All the time he was helpless as they piled in with their feet.
"A lone police officer stopped the attack and bravely chased off the four jacked-up lads. As they ran away, Billy Holland was tripped by a member of the public."
The victim woke up a broken jaw with no memory of the attack. He had to be put in a medically-induced coma by doctor's and could not return to work for five weeks.
Police tracked down and arrested the cousins. They found blood on Kieran Holland's shoe.
They were found guilty by a jury on March 23, during which they heard how Billy Holland had lied about his involvement and claimed to throw the first punch. They pair have never revealed who the other two attackers were.
In mitigation, their barristers pointed out that neither had touched alcohol or reoffended since the attack three years ago.
Mr Butterfield said: "Both of you still deny the offences you have been convicted of. You are both young and you were in drink. It is sad that you, Billy Holland, had no previous convictions before this attack."
For his part in starting the attacked, Kieran holland was sentenced to five years in a young offenders institute.
Billy Holland was sentenced to one year in a young offender's institute.