Anne Marie Bates had always doted on her younger brother Aaron. Pictures lining the walls of their family home capture the blond boy and his smiling older sister. As with many families, their parents have endless stories about Anne Marie's protectiveness over "her baby".

But now the photographs simply provide stark reminders of both their untimely deaths. In separate moments of deep despair, the brother and sister chose to take their own lives. Anne Marie was 19, her brother 12. Their deaths followed the attempted suicide of their older brother.

During the past few weeks, an inquest into Anne Marie's death has pieced together the final few hours of her life. The hearing heard that, five years ago, she found herself on remand in an adult prison for a robbery charge, despite the judge's recommendations that the vulnerable 19-year-old should be in a bail hostel. She had given birth two weeks earlier and was struggling with drug addiction as well as being bullied by other inmates.

A few weeks later, after feeling increasingly desperate over her separation from her third baby, she was found hanged in her prison cell.

For her parents, the news of her tragic end was the latest in a horrific series of deaths in a family that had been unremarkable until their eldest son, Robert, was placed in a young offenders institute at the age of 17.

Anne Marie was 12 at the time, loud and sociable with ambitions to become a nursery nurse, when Robert was detained at the Brinsford Young Offenders Institute in Wolverhampton, on suspicion of car theft. It was there that he was founding hanging from bed sheets in his prison cell.

He survived but his injuries were so severe that his parents, Violet and Ron Brayson, were told he would be in a permanently vegetative state for the rest of his life.

Violet, who lives in Birmingham with her husband and family, said that was the turning point for all of her children and that the shock of Robert's changed state "broke" the family.

"He can't communicate in any way. He breathes through a tube. He is fed through a tube. It hit everyone very hard. Aaron was only six, and he had been very close to his brother. Neither him nor Anne Marie could believe he went away normal and came back like this. They were still babies themselves and we had to be in hospital for Robert so much, it must have affected them. Aaron said he wanted his brother back the way he was when he went to see him in hospital. He was too small to understand," she said.

Violet and Ron took on Robert's full-time care, and began a long legal battle to discover what had led Robert to apparently hang himself, suspicious that many of his injuries were not consistent with hanging.

"To this day, we have not had closure over what happened to him. We would like his case to be reopened in court. If that were sorted out, we could get on with our lives," said Violet.

"The children had such a sadness in their eyes. They were destroyed by it. But we were caught up fighting the system. We were all upside down," said Ron.

Anne Marie coped by running away from the situation, and went "off the rails", according to her parents. "She needed closure over what happened to Robert," said Violet, adding, "We all did."

Some years later, when Aaron was 12, his mother came across his school books which illustrated how, in one lesson, he was forced to examine "how evil suicide was" and he had drawn pictures of hangings, said Violet.

Then, one night, after chatting with his mother until the early hours, Aaron went up to his room and in a chilling imitation of his brother's hanging in prison, hanged himself in his bedroom.

But, unlike his brother, he didn't survive. His death left the family, already struggling to cope with tragedy, destroyed.

"I believe that he didn't mean to kill himself. It shouldn't have happened. The way Robert changed really affected him. He looked up to Robert, he just adored him," said Violet.

"Anne Marie just went snap. She went into self-destructive mode when Aaron died. She was running away from home before Aaron's death .She was dabbling with drugs. When he died, it finished her off. She got into harder, heavier drugs. She got involved with prostitution because of the drugs. We were trying to get her into rehab. She was 17 by then. She was fighting against the drugs just to get to Aaron's funeral," added Ron.

By the time Anne Marie encountered the criminal justice system, everyone should have known how vulnerable she was.

She had had her first child, a daughter, now aged nine, when she was 15 years old. By the time she appeared at Birmingham Crown Court in July 2001, she also delivered a premature son, now seven, and given birth to another son, now five, two weeks previously.

Anne Marie's inquest jury sitting in Stourport-on-Severn, Worcestershire, was told that a judge hearing her case at the crown court had suggested that she be placed in a bail hostel if a space became available.

But she was kept in a Category A wing of Brockhill Prison, near Redditch, in Worcestershire, and was given no care plan despite being identified as a high risk of suicide and self harm.

In the final month of her life, she was struggling with the effects of withdrawal from drugs while also being bullied.

Yesterday, her inquest jury returned a verdict of "accidental death by applying a ligature to herself while not intending to take her life" but listed a series of failings by the prison system as contributory factors to her death, including the fact that her placement on A wing was "inappropriate due to her vulnerability", that there was "inadequate support for Anne Marie to deal with the bullying on A wing".

The jury also found that an "inappropriate relationship between a prison officer and an inmate" which Anne Marie discovered while she was in Brockhill, was "the driving force behind her inappropriate transfer to A wing".

Her distressed state of mind over her bail conditions and her deep concern over her baby son, who had been placed in foster care with very limited access to her, also contributed to her death.

Helen Shaw, co-director of the Inquest campaign group, said she was dismayed by Anne Marie's sad story. "It has taken nearly five years for this tragic and unnecessary death to be subject to public scrutiny is unacceptable. The evidence heard at the inquest demonstrates clearly that Anne Marie did not receive the care she needed in the final days and hours of her life.

"Following the highly critical verdict and damning evidence heard at the inquest, it is crucial the Prison Service make a statement about what steps they will be taking to hold to account those staff who failed Anne Marie.

"The inquest and investigation system must be reformed urgently to ensure other families do not wait for so long to find out the truth and that action is taken so that more women do not die in similar circumstances,"she said.

Ironically, her parents feel she was more determined than ever to turn her life around days before her death. But dangerously, she was also at her most emotional and had been identified as a vulnerable case.

In her many letters to her mother from prison, she spoke of her hopes for a reunion with her baby, and how terribly she missed him. "She wrote and phoned and said she'd had enough of the drugs. She wanted to clean up. She wrote me a letter asking me if she could come back home and live with us. I said of course she could. She wanted to get her baby back and start her life again.

"The most vulnerable time for a woman is after the birth of a child. She was waiting and waiting to go to a bail hostel. She was desperate to see more of her son] but he'd been taken into care and when he was put with a foster family, they took him on holiday with them so she had no access," said Violet.

In her final conversation with her mother, she again vowed to come off the drugs and move back into her parental home. Shortly before her death, Violet and Ron decided to take a holiday - the first they had taken in years. A few days into the trip, the couple received a phone call from Violet's sister. "When we got the phone call, it felt like too much. We hadn't even properly mourned Aaron and we were losing another child," said Violet.

Her ashes, just like Aaron's before her, were placed in the family crypt in Gibraltar, where Violet's extended family live.

For those clamouring for more convicted criminals to be locked up, Anne Marie's story is a powerful riposte. Home Secretary John Reid has announced plans for more jails as Britain's prison population reaches record numbers. For Anne Marie's parents, such measures are difficult to comprehend.

Yesterday, as they expressed their relief at the inquest's verdict, the questions - and the anger - remained. "We always knew Anne Marie should not have died. We have been waiting for five years and the inquest vindicates what we have always believed. We are grateful some prison officers had the courage and honesty to come forward and tell the truth," said Ron. "We still want to know what will happen to those prison staff who failed Anne Marie.

"What really matters is Anne Marie died and nothing will bring her back. At least she didn't die with her secret."