Police are investigating how an adult brother and sister died after their bodies were found in separate rooms in a home in Brisbane's south on Tuesday.
Officers were called to the home at Macbeth Place in Sunnybank Hills, at 2:30pm on Tuesday.
Police said the woman, 58, and the man, 54, were believed to have been dead for some time.
Investigators said their 89-year-old mother found the pair and alerted neighbours, who called triple zero.
Senior Sergeant Gary Aschenberger said it was too early to tell the cause of death but said autopsies were being carried out today.
"[That is] unknown until forensics have been through there and obviously autopsies will be conducted as well," he said.
He would not say if the deaths were being investigated as murders, saying "nothing was being ruled out".
Forensic police and detectives from the Criminal Investigation Branch have been investigating what caused the deaths.
Neighbours 'shocked', saddened by deaths
Neighbour June Lee has lived across the street from the house for the past two years.
"They were quiet, very quiet — it's not a very social neighbourhood," Ms Lee said.
"I'm very shocked, it's a nice, quiet neighbourhood, very open.
"I haven't seen them many times but the man would say hello when he left the house.
"A few times, I saw the [older] lady sitting in the front yard of their house."
She said two weeks or so ago, the older woman came to her house to ask to call a locksmith when she was locked out.
It is understood, from conversations with neighbours, that the 89-year-old woman had no mobile phone and was very dependent on the children.
Another neighbour said she had to call a taxi for the son and his mother to go to the nearby Sunnybank Hills Plaza shops.
Ms Lee said sometimes the children would take their mother for a stroll through the neighbourhood and would stop and sit on her front lawn.
"She [the sister] was the main carer because the mum was very old — it was hard for her to move without help and the brother is a little bit challenged," Ms Lee said.
"I feel so sorry about this — I hope she [the mother] has more friends or relatives."
Ms Lee said last Wednesday was the last time she saw activity at the house.
"The daughter wouldn't normally take the bins out but I noticed last week the bins stayed out for [a] very long time," she said.
"I thought they must have been on holidays, then the bin moved back in."
