Craig Robins, a 27-year-old wheelchair user, was attacked in his car in Lomax Road, Hednesford, in October 2006.
He had been searching for people he thought had damaged his adapted Vauxhall Astra.
Mr Robins never regained consciousness, entering a coma after the attack and dying aged 40 in 2019.
Bernie Peter Smith and Kyle Neil Smith, aged 30 and 33 respectively, were both found guilty of manslaughter on Tuesday after a one-week trial.
The brothers will be sentenced at a later date along with two other men - serving prisoner Gavin Brown and James Ainsley Milligan of Hednesford Road, Cannock - who had already admitted killing Mr Robins.
Stafford Crown Court had been told how co-defendants Bernie and Kyle Smith, who both pleaded not guilty to manslaughter, were part of a group involved in an attack where the victim was stabbed, punched and kicked.
Prosecuting barrister Mr Jeremy Benson QC said the victim died as a result of sepsis, or blood poisoning, after being attacked by the Smith brothers and two other men – Brown, who pleaded guilty to murder and Milligan, who pleaded guilty to manslaughter.
Jurors in the trial heard how the attack led to the coma and "irreversible" brain damage. After a long stay in hospital, Mr Robins was cared for by his family at home 24 hours a day.
Mr Benson said Mr Robins, who had been paralysed from the chest down after a serious car accident in 1997 when he was 19, believed he had been targeted because he was disabled.
He said that the car had been broken into before and on October 30 he reported to police that the vehicle's tyre had been slashed while parked on the drive of his Hednesford home.
This led to Mr Robins taking machete around the Hednesford estate looking for the people responsible, a judge heard.
Kyle Smith told the court he was "scared" of his alleged victim – and had punched Mr Robins once after being told by teenagers at a party a man was outside making threats, saying he had a gun and brandishing a machete.
Jurors at Stafford Crown Court retired to consider their verdicts on Friday morning and returned unanimous guilty verdicts on Tuesday.
Bernie Smith, 30, of Rowley Close, in Hednesford, and Kyle Smith, 33, of Pebble Mill Drive, in Cannock, will be sentenced at a later date along with Brown, 36, of HMP Lancaster Farm, and Milligan, 42, of Hednesford Road, Cannock.
The three men convicted of manslaughter were released on bail ahead of sentencing but were warned by the judge to expect to be sent to prison. Milligan is already behind bars.
Detective Sergeant Katie Gregory, of Staffordshire Police's major investigations department, said: “This was a tragic case and we would like to offer our condolences to Craig’s friends and family.”