A 17-year-old girl called police after escaping from her family's California home where she and her 12 brothers and sisters were locked up, some so malnourished officers at first believed all were children even though seven are adults.
The girl, who was so small officers initially believed she was only 10, called 911 and was met by police who interviewed her and then went to the family home in Perris, about 70 miles southeast of Los Angeles.
They found several children shackled to their beds with chains and padlocks in dark, according to the Riverside County Sheriff's Department.
The children, ages two to 29, "appeared to be malnourished and very dirty," according to officers who arrested the parents.
David Allen Turpin, 57, and Louise Anna Turpin, 49, each were held on $9 million (£6.5 million) bail and could face charges including torture and child endangerment.
David's parents, James and Betty Turpin, told ABC News they were "surprised and shocked" by the allegations and could understand "any of it".
They said that they are considered to be a good Christian family in their community and that added that "God called on them" to have as many children as they did.
The pair also said their grandchildren had "very strict homeschooling," and they would memorise long passages of the Bible, some of them aimed to learn the entire Bible.
James and Betty told ABC News the last time they saw the family was in California four to five years ago. They said the children "looked thin," but they seemed like a "happy family."
James and Betty added that they did speak with David and Louise on the phone since the visit, but they had not spoken to their grandchildren, because David or his wife would usually call when the children weren't around.
Neighbours said they were stunned by the arrests. Andrew Santillan, who lives around the corner, heard about the case from a friend.
"I had no idea this was going on," he told the Press-Enterprise of Riverside. "I didn't know there were kids in the house."
Other neighbours described the family as intensely private.
A few years ago, Robert Perkins said he and his mother saw a few family members constructing a Nativity scene in the Turpins' front yard. Mr Perkins said he complimented them on it.
"They didn't say a word," he said.
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