Avril Boyle, from Finglas in north Dublin, said she discovered her brother Ian Brady was living on the streets after she saw him outside St James's Hospital a few weeks ago.
"I'm sick myself; I have breast cancer and bone cancer and I was in hospital myself a few weeks ago and this is how this all started."
She said after attending a hospital appointment she saw someone lying on the ground on cardboard near the hospital and was shocked to realise it was Ian. When I saw him, I almost died. I didn't know him."
She said Ian (51) previously worked as a courier and had a flat with his girlfriend, but his life spiralled after his girlfriend died tragically.
"He has been in and out of hostels for a few years. When he was in hostels we knew where he was."
After she discovered Ian was living on the streets, Avril spoke to the Simon Community who came to help him and brought him to a hostel but Ian wouldn't stay and returned to the streets.
"I think something happened in one of the hostels. The man from the Simon Community said he was very vulnerable and he was terrified.
"Ian won't tell us what happened but I think something happened to him in a hostel and he's too afraid to go back. I can't take him in because I'm sick and don't have the room because I only have two bedrooms."
She said she has been trying various homeless charities and politicians but so far hasn't been able to get him off the streets.
"There's places in hostels but he's too scared to go back in.
"I've tried to apply to get him housing but they said he has to apply himself and he's not capable of doing that at the moment.
"I rang a few places during the week and said to tell him to go to Hap [Housing Assistance Payment]. How can he go to Hap he has no address? I asked if they could send a form to me so I can fill in it or get him to fill it in but they won't do that.
"We're caught everyway we go. It's Catch-22. I wanted to tell this story because maybe someone will know what to do to help him. Any kind of a place, whether it be a B&B or anything. Just somewhere where he can have a room on his own."
She said Ian has also been in poor health recently.
"He's medically sick as well but I don't know what's wrong with him. He can barely stand up. He said he thinks he's dying.
"He's going to be found dead and I don't know what to do."
Avril and her husband have been visiting Ian on the streets to bring him clothes and food, but said he keeps getting robbed by other people living rough.
"My husband gave him clothes and a phone with credit on it so he could ring us.
"The phone was robbed later that night. He rang me at 7pm that night and the phone was robbed by 11pm. It was gone."
She said all the clothes she bought him were also robbed.
"He's being robbed and he's not able to stop them."
She said she had also been bringing him food over the past few weeks and while he was eating initially when she visited him on Friday, he couldn't even eat food or drink tea that she got for him.
"My brother is going to be found dead on the ground. He's going to freeze to death. It's already very cold and we're not in the depths of the winter."
"When you talk to him, he's not on our level. I told him he needed to get up off the ground and go to a hostel and he said he just wanted to die. There's no fight left in him anymore."
Ian told the Sunday World that he was in a lot of pain but didn't know what to do.
"I can't get up. I can't walk or anything. I'm f***ed up. I probably shouldn't be here but there's not a lot I can do. I don't know what the right treatment is for me. Avril is trying to help. I'm just on the street here, I can't even change my clothes anymore."
Avril added: "He just wants a place to call home where nobody is robbing him. He said he can't close his eyes in the hostel. Everything he has is gone.
"I know this isn't just happening to my family, it's happening to loads of families. I'm not pushing this at anybody. I'm not pushing this at the council or Simon community or Merchants quay or anybody. I'm just trying to figure out is there someone out there who can do something for him."
Figures released this week revealed there has been a significant increase in the number of homeless people in recent months.
The number of men, women and children in emergency accommodation increased by 355 to 8,830 over the month of October.
Homeless charities described the trend as worrying and said Christmas will be a particularly challenging time.