Fresh details have emerged of the 13 California siblings who were kept in “horrific” conditions by their parents.

David Allen Turpin, 57, and Louise Anna Turpin, 49, were each charged with nine counts of torture and 10 counts of child endangerment.

The siblings are being treated after an ordeal that authorities say could leave them scarred for years.

Some of them were found shackled to furniture; others were starving and malnourished.

Authorities were alerted after one of the children, an emaciated, 17-year-old girl, called police after escaping through a window of the house in Perris, 115 kilometres east of Los Angeles.

The teen, who was so small that deputies initially thought she was 10 years old, showed them photographs that led them to believe her story so they went to the home to check on the family.

The children rarely left their dishevelled house and, when they did, appeared small and pale and acted strangely, neighbours say.

David and Louise Turpin were arrested on Sunday.

Police said they found several of the couple’s 13 children, ranging in age from two to 29, “shackled to their beds with chains and padlocks in dark and foul-smelling surroundings”.

“The victims appeared to be malnourished and very dirty,” it said.

Kimberly Milligan, who lives across the street from the family, said she only saw the infant in the mother’s arms and three other children since she moved in across the street two years ago, describing them as small and pale.

“Why don’t we ever see the kids?” Milligan said she asked herself.

“In hindsight, we would have never thought this. But there were red flags. You never don’t hear or see nine kids.”

Six of the couple’s children are minors, while the other seven are over 18, police said.

The family has lived at the house since 2014, where they home-schooled their children, police captain Greg Fellows said. Six of the couple’s children are minors, while the other seven are over 18, according to neighbours.

The parents home-schooled the children strictly and required them to memorise long passages from the Bible, David Turpin’s parents, James and Betty Turpin of West Virginia, told US TV.

The Turpin address was listed by the California Department of Education as the location of the Sandcastle Day School, with David Turpin as principal.

In 2010, David Turpin left his job at Lockheed Martin , a company spokeswoman said. He also worked as an engineer at Northrop Grumman, the aeronautics and defence company.

David and Louise Turpin appeared to have had marriage-renewal ceremonies at least three times, in 2011, 2013 and 2015, at an Elvis Presley-themed chapel in Las Vegas, according to the chapel’s YouTube page.

One video shows the couple exchanging renewal vows in front of an Elvis impersonator.

Another video showed 10 female children in matching purple plaid dresses walking down the aisle ahead of Louise toward David, who waited anxiously at the altar with two male children in suits.

A third male child dressed in a suit appeared later in the video during various dance performances with the Elvis impersonator and the family.

An Elvis Chapel representative did not immediately respond to a request for comment.

A joint Facebook page that appeared to have been created by the parents showed the couple at the same chapel dressed in wedding clothes, surrounded by the 13 children.

The siblings told officers that they were starving when found, police said.

Two years ago, while walking around the neighbourhood admiring Christmas lights and decorations, Milligan said she encountered three of the Turpin children and complimented them on the manger with a baby Jesus set up outside the house. She said the children froze, as if by doing so they could become invisible.

Nicole Gooding, who has lived in the neighbourhood for three years, said the first time she saw the family was two months ago when the mother and children were cleaning up the yard that was full of weeds and overflowing trash cans.

The parents, who were scheduled to appear in court on Thursday, are being held on $US9 million ($A13 million) bail each, police said.

-with AAP