The sister of House of Horrors mother Louise Turpin has told how they were both sexually abused by their grandfather as children.
In her new book Sister of Secrets, Elizabeth Flores tells how Louise, who is older than her, protected her from the man they called "Papaw" by submitting herself to abuse so that she did not have to, the Daily Mail reports.
"I would come to know his silky, persuasive voice as a sign of what was to come, later in my years.
"But my sister knew what this dark-haired man standing tall with authority beside us wanted.
"Turning to me, she looked at me with tears in her eyes and said, 'I'll go'. She was my protector; my shield," she said.
She continued to allege that the man carried out the abuse as their younger sister Teresa watched. There was one chair. He sat down on the chair and put me on his lap.
"Poor little Teresa was forced to watch. She was about 4 years old because by this time I was about 9.
"I can remember her crying in the dark room while Papaw did stuff to me because she had no choice but to watch. She knew what was coming next," she wrote.
In April, Teresa said the three sisters had been abused by a male relative as children.
She said their mother was aware and that she had also been abused by him but that she forced them to go because he would give her money to feed them.
Flores claims in her book that her mother knew about it, as did their grandmother. While her grandmother divorced him after walking in on him abusing Louise once, Flores claims their mother forced them to endure the abuse.
"I knew Mommy was letting it happen because we were told that we had to go," she wrote.
Elsewhere in her book, Flores claimed that Louise, who left home at 16 to marry her husband David, became obsessed with witchcraft.
Louise remains in custody on multiple charges of child abuse along with David.
She is not facing any sexual abuse charges but David is accused of one.
They were arrested in January after one of their emaciated children escaped their home and asked for help.
At some time between 2008 and 2010, Turpin went to her sister's home in Texas and brought an Ouija board with her, Flores said.
She told her sister that it told her she would have another baby.
"She told me she was messing around with witchcraft. It just really freaked me out.
"She brought the Ouija board to my home and I wouldn't let her bring it in my door," Flores told The New York Daily News on Thursday as she promoted her new book, Sisters of Secrets.
Afterwards, she tried to convince her to join a snake-handling festival and believed the reptiles would give her "power".
"Louise was attracted to that, like women dancing with rattlesnakes around their necks.
"She was reading that snakes give you power," Flores said.
Flores believes that it played a role in her sister's treatment of the children who all required hospital care when they were saved because they had been starved and mistreated so severely.
"I do know witchcraft is very serious and demonic.
"If she did get deep into that, I do think it could have led her to do what she did because you're basically selling your soul to the devil.
"Maybe she was the mastermind behind all of this. Maybe it wasn't David," she said.
Flores, who did several interviews after her sister's arrest in January, said she wrote the book to give their abused children a "voice".
"I want them to read the book and know they do have a voice.
"My nieces and nephews didn't know they had a voice," she said.
She is not the only one of her siblings to speak out since the pair's arrest made international news in January.
Teresa Robinette, their other sister, has told how their own mother allowed a paedophile to rape them when they were children, in return for money.
Turpin and her husband both deny the 50 charges of abuse they stand accused of.
When their children were found in January, some were chained to their beds. Some had never been to a dentist and they were severely malnourished.
Turpin and David remain in custody on US$2million bail.
They had moved around for years before the children were found, displacing them from state to state which is how authorities believe they evaded detection.
In a recent court appearance, David Turpin denied perjury for allegedly lying to authorities by claiming the children were enrolled in school.