Photos provided by the Riverside County Sheriff's Department show Louise Anna Turpin, left, and David Allen Turpin. Picture: Riverside County Sheriff's Department via AP

California - The odd behaviour didn't escape the neighbours, but maybe David and Louise Turpin were simply an odd couple with a big family who preferred to be private.

One neighbour, Mike Clifford, didn't worry too much when he saw several children walking in circles late at night inside their Southern California home. It was strange, he told the Los Angeles Times, but maybe it was just something they did, or perhaps the children had special needs.

Another neighbour, Salynn Simon, told the Times that she was surprised but not disturbed when she met one of the Turpins' sons, a man in his mid-20s who didn't look his age. "You look 15," she told the young man who only smiled and nodded.

Neighbours and family members now know there's more to the Turpin family than just odd behaviour and that the couple's children were malnourished. The harrowing revelations of the past few days captured headlines around the country and elsewhere. "HOUSE of HORRORS," read a headline on the cover of People Magazine. The revelations also confounded those who had interacted with the couple and left some grappling with why they weren't more concerned at the time.

Authorities said the children, for reasons still unclear, were starved for years and held captive in a dirty, smelly house in Perris, California, not far from Los Angeles. If they misbehaved, they were tied to their beds as punishment - first with a rope and later with chains and padlocks - and were kept from using the bathroom, Riverside County District Attorney Michael Hestrin told reporters last week.

The pervasive child abuse hid in plain sight for years and was not uncovered until last week when one of the couple's daughters slipped through a window and called 911 from a phone she found inside the house, the Riverside County Sheriff's Department said. She said she was 17 years old, but she was so tiny that authorities thought she was only 10. Deputies were equally shocked to find that several of the Turpin siblings were, in fact, adults.

The Turpins had 10 girls and three boys. The oldest is 29 and weighed only 82 pounds. The youngest is 2, the only one of the siblings who weren't malnourished, officials said.

The Turpins are each facing nearly 40 charges, including a dozen counts of torture and another dozen counts of false imprisonment. Riverside County Superior Court Judge Emma Smith Wednesday barred the parents from contacting their children for the next three years, including by phone or electronically. Only their lawyer can deliver messages, The Desert Sun reported.

The case's national press coverage over the last week has led David Turpin's attorney to consider asking if the trial could be moved outside of Riverside County.

"The frequent appearance of photographs or video imagines of the Turpins in the media may taint potential jurors, prejudice them against the Turpins and make it necessary to explore a possible motion for a change of venue," Attorney David Macher wrote in a court motion, according to The Desert Sun.

Read: 'Tortured' Californian siblings set for a long, hard road to recovery

People who knew members of the Turpin family are now reexamining their interactions with them.

A man who said he attended elementary school in Fort Worth, Texas, with one of the Turpins' daughters remembered a frail girl who wore the same dirty purple outfit every day and tied her hair with a Hershey's bar wrapper - the girl "nobody wanted to be caught talking to".

The man, Taha Muntajibuddin, now 28, said the girl moved away after third grade. Years later, he said, he found himself wondering how she was doing. He had a "rude awakening" last week after reading stories about the girl and her family, he said.

"I can't help but feel an overwhelming sense of guilt and shame. Of course, none of us are responsible for the events that ensued, but you can't help but feel rotten when the classmate your peers made fun of for 'smelling like poop' quite literally had to sit in her own waste because she was chained to her bed," Muntajibuddin wrote in a lengthy Facebook post. "It is nothing but sobering to know that the person who sat across from you at the lunch table went home to squalor and filth while you went home to a warm meal and a bedtime story."

The family had also lived in Murrieta, California, where Clifford said he often spotted the children through a window on the second floor at night. They would march in circles, over and over, for long periods of time, he told the Los Angeles Times.

"It was kind of strange, [but] there was never anything to say, 'Oh, my God. I should call somebody,'" said Clifford, who did not immediately return a call from The Washington Post.

Other nights, he saw the siblings getting into a van with their father, he told the Times. Again, he wondered why but didn't suspect anything horrendous.

The family moved a few miles north, to Perris, in 2014. There, during a Christmas decorating contest two years ago, Louise Turpin gleefully talked about her big family and joked about how her older children always had to show their IDs during trips to Las Vegas, Simon, the other neighbour, told the Times.

Read more: 'Very normal' US parents charged with torture of 13 children

Turpin had always wanted a big family and gushed about "Kate Plus 8," a reality show about a mother and her sextuplets and twin daughters, Turpin's brother, Billy Lambert, told People. She was even talking about having a 14th child.

If he and other family members had known something was wrong, Lambert said, they "would have stopped it ourselves."

On the surface, the family seemed happy. The Turpins renewed their wedding vows at least three times since they were married 33 years ago. One was as recently as 2015 when the couple slow-danced to "Can't Help Falling in Love" sung by an Elvis impersonator. Louise Turpin wore a white, strapless wedding gown and her husband, a tuxedo. Their daughters were in matching purple plaid dresses with ribbon belts and their sons in identical black suits and red ties.

Some photos online show the Turpins on family trips, always wearing identical outfits. In one picture, the siblings - all pale and skinny and wearing the same red T-shirts with different numbers printed on the front - smiled as they posed with their parents.

"She would tell us the kids are doing great. She was real busy home-schooling," Lambert told People. "She told us David was making two or three hundred thousand [dollars] a year, so we thought they had this awesome life and always going on trips."

Records show the Turpins were thousands of dollars in debt. They filed for a Chapter 7 bankruptcy at least twice - in 1992 in Fort Worth and in 2011 in Riverside, California. Court documents say David Turpin made about $140,000 as an engineer while his wife stayed at home.

Records also show that the Turpins ran a school from their home. David Turpin is listed in a state Department of Education directory as the principal of Sandcastle Day School, a private K-12 school that has the same address as the couple's home.

The Turpins, who are each being held on a $12 million bail, are due back in court Wednesday afternoon. Prosecutors are seeking a protective order to keep them from contacting their children, all of whom have been removed from the home.

The Riverside University Health System Foundation has started an online campaign to raise money to help the siblings. "Our phones started ringing almost immediately with calls from private individuals and organisations wanting to know how they can help," Erin Phillips, the foundation's executive director, said last week. "We recognise financial gifts will not eliminate the trauma, but additional resources will be extremely important in helping these victims adjust over time."

The Turpins are next due in court on February 23.