A court heard Lewis and Reece Morley left the victim with broken ribs and a fractured eye socket after they took exception to his "uncouth" behaviour.
Robert Stevenson, prosecuting, said the attack took place on February 16, 2020.
The brothers' mum met the victim on an internet dating site in the two weeks leading up to the incident.
They arranged to meet for the first time and she gave him her daughter's address in Leeds where a party was being held.
Mr Stevenson said the man drove to the house in his Audi and he chatted with the Morleys' mum inside the vehicle before he was invited into the property.
During the evening the brothers became angry as the victim danced with her.
One of the defendants accused him of "taking the p***' and said: "That's my mum."
The mum told her son to calm down and said the victim had done nothing wrong.
The man left the house, got into his car and lit a cigarette.
He was attacked as he was about to drive away.
The defendants and a third man opened the doors to the car and began to punch him.
He was then pulled from the car and punched to the head and body as he was on the ground.
Mr Stevenson said the victim may have lost consciousness during the attack.
He managed to get up and ran to a petrol station.
The prosecutor added: "He was terrified because his eye was swollen and he could not see very much."
A member of staff at the petrol station contacted the police.
Officers took him back to the house to get his car but the vehicle was gone.
Lewis was arrested the following day when police officers saw him running away from the Audi.
Reece was arrested two days later.
Both men were identified as the attackers by the victim.
The victim's blood was recovered from the defendants' shoes by forensic experts.
Both defendants refused to comment during police interviews but later pleaded guilty to inflicting grievous bodily harm.
The victim suffered a fractured eye socket, broken ribs and cuts and grazes to his head, hands and body.
He provided a statement to the court describing how he had been left with permanent scars
Mr Stevenson said: "He is reminded of the attack every time he sees the marks."
Stuart Field, mitigating for Reece, said: "He had no reasonable right to behave as he did but he took the view that the complainant was behaving towards his mother in an uncouth and not very attractive way and he took exception to that.
"He took the view that his mother was being humiliated by the way the complainant was behaving."
Jane Cooper, mitigating for Lewis, said it was accepted that the defendant had been "overprotective" towards his mum.
Ms Cooper said Lewis had been in custody for the past eight months,
Reece, 24, of Slingsby Crescent, Harrogate, was given a 22-month sentence, suspended for 18 months.
He was ordered to pay £1,000 compensation to the victim.
Lewis, 22, of Lincombe Drive, Roundhay, was made the subject of a 12-month community order with 30 rehabilitation activity requirement days.
Sentencing, Judge Rodney Jameson QC said: "There was a party and a good deal of alcohol was taken.
"The complainant was acting in a relatively intimate way with your mother.
"He was entitled to do that because she wanted him to. But you saw it differently.
"You decided to take the law into your own hands.
"When the complainant went outside you went after him and beat him up. It is as simple as that."