Jason Dixon, aged 47, was found dead at the St Wilfrid's supported living centre on Queens Road on September 27, 2019.
An inquest into his death was opened last April and found that he had suffered severe frostbite after spending a night outside and that he had died from a blood clot in his lung.
But he was not homeless or a drunk, said one of his sisters Kerry Cocking, 44, who deemed Jason as "the life and soul of any party".
She said on the night he got frostbite on his feet, he was not homeless but only went on a "four-day bender" after he failed to meet his daughter who was under the care of his ex-wife in Sheffield
"He took himself out the night he went missing not even knowing what he was doing. He had no shoes on and not even a jumper or a coat.
"He was missing for some four days and was only found by passers by: when they found my brother all he had on was his Liverpool shirt.
"He was about an hour away from death. He was found down a disused railway embankment. I was told this myself by the police.
"He was in hospital for a while where the Northern General Hospital discharged him knowing he at that point had nowhere to live.
"His best friend and partner took him in until he found a place at The Greens where he stayed for a while and broke the rules so was asked to leave, this is when he moved into St Wilfreds where he met his untimely death."
Jason's older sister, Carol Napier, 51 said Jason had always kept in touch with her and Kerry, even on the night of his death. She said Jason had lived with her in Kingsland before he went to Sheffield.
During the inquest, Great Places, which managed St Wilfrid's Centre where Jason was, admitted there had been an internal investigation after it was discovered a mandatory risk assessment and well-being with Jason had not taken place.
Carol said if not due to the system failure, his brother would not have met his death and he would've still been able to return to his family.
"We'd push further by taking it to court. They've changed the policies and procedures since but have that all been in place when my brother first moved in, I believe he'd still be alive.
"The carer couldn't turn up on the night he died when the place was supposed to be manned 24/7 but the carer was not given the keycode.
"Why wasn't the carer given the keycode to the building of someone who's vulnerable, in a wheelchair, bipolar and has problems with drug medication and alcohol?
"Despite all that, nothing in his system indicated that he had taken drugs or alcohol (during the post mortem)."
Kerry said: “His marriage was broken. He was depressed inside because he hadn’t got his baby girl, but he was the life and soul of any party.”
St Wilfrid’s Centre has been contacted for comments.