Gareth Leach, 28, and Kyle Martin, 22, battered Dean Williamson, 45, at his home after he had stolen the disability aid from their mother, Sara Martin, 50.
Jurors heard how the half-brothers kicked and stamped on Mr Williamson outside his house in Rotherham, South Yorks., causing him to lose consciousness.
Mr Williamson died in hospital hours after the attack on October 5 last year. He'd suffered facial and chest injuries in the attack.