The beatings and forced restraint may have contributed to 50-year-old Adrian Casey's death on New Year's Eve 2018, a coroner said at the inquest at Wakefield.
Wakefield Coroner's Court was told Mr Casey pointed a realistic-looking imitation firearm at Daniel and Ian Ward's mother after breaking into their home on Rosgill Drive, Seacroft.
The inquest heard Mr Casey had demanded money but was eventually restrained by the two brothers, who repeatedly punched him.
Ian Ward, the older of the two brothers, sat on Mr Casey and held his face against the road outside their home for around 20 minutes while waiting for the police to arrive, the inquest heard.
But he and his brother eventually stopped restraining the intruder when it became clear the man was no longer struggling, witnesses said.
Despite being treated by police and a paramedic, Mr Casey was declared dead a short time later.
The inquest was told that Daniel and Ian Ward had both been arrested and charged with murder following the incident.
But proceedings against them were dropped when a post-mortem examination report was unable to attribute a single, definitive cause of death.
The inquest was told that, in a police interview conducted days after the incident, Ian Ward said he and his brother had repeatedly hit the intruder, but he denied murdering him.
The inquest heard Ian Ward said in the interview: "Obviously he's come into our house and attacked us, waving a gun at my family, so I was defending myself and my family.
"I did not want to kill him."
In his police interview, Daniel Ward said that on the day of Mr Casey's death he was in the shower when he heard a commotion downstairs at around 5pm.
He said he went downstairs and saw the trespasser, who was with an accomplice, holding a gun to his mother's head and demanding money.
Mr Ward said he believed that he and his brother's actions in restraining him "were justified", adding that he had punched Mr Casey "with a bit of force".
Charges against the brothers were dropped when a post-mortem examination report by forensic pathologist Dr Kirsten Hope gave a number of potential causes of death.
The report, the inquest heard, said Mr Casey, of Seacroft, may have died as a result of a blunt force head injury, through heart disease, a slowing down of the heart as a result of amphetamine use, as a result of restraint, or through a combination of these factors.
The inquest heard Mr Casey, who worked as a joiner, also had a brain malformation which could have increased the chances of sudden death.
In a statement read out at the inquest, Mr Casey's partner, Louise Casey, said: "The Ward brothers enacted a sustained assault on Adrian, and they went too far in their assault on him.
"The Ward brothers are walking around living freely, while the lives of myself and my family have been destroyed."
She said the father-of-one had been born Adrian Bennett, but was estranged from his family and changed his surname in 2006 to match hers because they believed they would marry.
Area coroner Jonathan Leach recorded a narrative conclusion, agreeing with Dr Hope's findings and saying the "assault" Mr Casey received "may have resulted in his death", but that other
factors identified in the post-mortem examination could also have been the cause.
At Leeds Crown Court in November 2018, Aaron Tinker and John Rowley, were jailed after being found guilty of conspiracy to commit robbery and possession of an imitation firearm in connection with the raid at the Wards' home.
Tinker, of Mill Green Road, Swarcliffe, Leeds was given a 14-year sentence and Rowley, of no fixed address, was locked up for 12 years.
Jurors heard how Rowley and Mr Casey were armed with a fake handgun when they burst into the house.