Their story is almost unimaginable - two sisters who for 25 years were raped by their violent father and bore him nine children.
Forced to live in isolation in various rural villages across northern England for most of their lives, their suffering went unnoticed until this year.
The shocking case of systemic incest has stunned Britain and sparked a top-level inquiry into why authorities failed to step in and save the sisters.
Details about the years of horror they endured came to light as their 56-year-old father - who along with his daughters cannot be named for legal reasons - was jailed for life on Tuesday.
The judge who heard the case in Sheffield Crown Court described it as the worst he had ever come across in his 40-year career.
Newspapers in the UK have dubbed the serial rapist the "British Fritzl", after Austria's notorious Josef Fritzl, who fathered seven children with the daughter he locked in a dungeon for 24 years.
While the two sisters were not imprisoned by their father, he did all he could to make sure they had little contact with the outside world so he could continue his campaign of terror.
The sisters' ordeal began when they were aged just eight and 10.
Over the years, they endured 19 pregnancies but only seven of their babies survived.
The eldest sister fell pregnant seven times and the youngest 12.
Ten babies were lost because of miscarriage or abortion, while two died on the day they were born.
Any time they begged their father to stop his attacks, he would beat and threaten to kill them and their children.
The case has provoked outrage from Prime Minister Gordon Brown and left British police, social workers and local councils scratching their heads about how the sisters went unnoticed for more than two decades.
The possible failures of the various authorities in detecting the abuse are now the subject of a wide-ranging independent inquiry.
"People will rightly want to know how such abuse could go on for so long without the authorities and the wider public services discovering it and taking action," Brown told parliament on Wednesday.
"If there is a change to be made in the system and the system has failed, we will change the system."
Details of the sisters' case emerged just a fortnight after a huge public outcry over the death of a 17-month-old toddler, dubbed Baby P.
The youngster died in August 2007 after months of sustained abuse involving his mother and her boyfriend, who were both found guilty on November 11 of causing Baby P's death.
The badly battered baby boy died despite 60 visits over an eight-month period by various authorities to his London home.
In the sisters' case, Sheffield Crown Court heard how their father had a "Jekyll and Hyde" personality and "took pleasure" in the harm he inflicted on his daughters.
At one stage he raped them every three days, forcing one daughter to babysit the other's children while he carried out his abuse.
Prosecutor Nicholas Campbell QC told the court the eldest sister had offered her father STG100 ($A233) a month from her child benefit payments to try to stop the attacks.
But her pleas failed, with her knife-wielding father telling her: "It's never going to end. You have to do what you are told."
"All the family were frightened of him," Campbell said.
"His younger daughter told of the frightening habit her father had of putting her head next to the flames of their gas fire and that when she struggled to get away on certain occasions she burnt her eyes."
The sisters' mother is believed to have left the family home soon after her daughters began being abused. She has denied knowing anything about her husband's attacks on them.
The man made his family move home repeatedly over the years, mainly to isolated villages in South Yorkshire and Lincolnshire, so the sisters would be unlikely to form friendships with any locals and alert them to their suffering.
In some villages, neighbours gossiped about how many children the sisters had despite not being married or appearing to have boyfriends.
At school, teachers questioned the sisters about the bad bruises covering their bodies but were told the injuries were inflicted by bullies.
And in GPs' surgeries, doctors repeatedly advised them to stop having children by the same father.
At all times the sisters were too terrified to reveal their terrible secret. When questioned by one doctor if their father was the father of their babies, they flatly rejected the claim.
In 1997 the sisters' brother, who fled home when he was 15, tried to raise the alarm but police dismissed his claims of incest as "hearsay".
A year later one of the sisters called a helpline run by the charity ChildLine and asked for a guarantee that she could keep her children if she came forward about the abuse.
But no guarantee was granted and the sisters' suffering went unreported.
Social service workers became involved with the family when they moved to South Yorkshire in 2004, but no action was taken.
When the father was arrested earlier this year, he initially denied raping his daughters but changed his plea to guilty when DNA tests proved their children were also his.
Relatives of the family have lashed out at what they say has been repeated failures of police and other authorities to protect the sisters.
"The police could have stopped it," the man's sister-in-law told the Sheffield Telegraph newspaper.
"They let those girls down. Our family has gone to the police a number of times over the years.
"We all suspected what was going on, did not agree with it, and it was reported to the police when the oldest daughter first gave birth.
"People may ask, `How could the family not do anything about this?' But we tried to get it to stop. We went to the police but nothing was done.
"They were always moving around whenever anyone got close and he thought the dirty secret would get out."
The sisters' father refused to face them in court this week when he was handed 25 life sentences with a minimum term of 19-and-a-half years.
According to The Times newspaper, he wrote to his brother from his prison cell, saying: "I haven't got any regret over what has happened. It's too late for that. It shouldn't have happened."
His daughters are now trying to rebuild their lives with their children.
In a statement released after their father was sentenced, they expressed relief that their harrowing ordeal was now over.
"His detention in prison brings us only the knowledge that he cannot physically touch us again," they said.
"The suffering he has caused will continue for many years and we must now concentrate our thoughts on finding the strength to rebuild our lives."
In the meantime, authorities have agreed to cooperate with the investigation into how the sisters' case went unreported for so long.
Director of children's services at Lincolnshire County Council and chairman of the Lincolnshire Safeguarding Children Board, Peter Duxbury, insisted child protection systems had improved.
"There has been a wholesale reorganisation of children's services and the establishment of a Lincolnshire Safeguarding Children Board, which provides effective management and ensures proper standards for the safety of children are maintained," he told the BBC.
"We will be cooperating with Sheffield in the completion of an independent review."
But Liberal Democrats leader Nick Clegg, who is also a local MP for Sheffield, has warned against the inquiry becoming "a witch hunt".
"I certainly think we shouldn't pretend or try and comfort ourselves that when someone does such evil barbaric things to their own family that there was some magic wand lying around 25 years ago that could have stopped him," he told BBC TV.
"Nonetheless, clearly questions need to be asked about whether the hospitals that the daughters must have come into contact with, the social services, the schools, whether they could have picked up any warning signals.
"But it mustn't become a witch hunt.
"If there were failings, if the independent review reveals that, clearly they need to be corrected."
