13 siblings held captive — how did no one else know?

A nondescript, burnt orange house in Southern California — similar to many others on the same street — turned out to be a prison for 13 siblings.

Now, questions abound over why the Turpin children were allegedly held captive by their parents — and how no one else seemed to know.

What we know
A 17-year-old escaped

If not for a daring bolt by a 17-year-old girl, she and her siblings might still be trapped.

The teen “appeared to be only 10 years old and slightly emaciated,” the Riverside County Sheriff’s Department said.

Using a cell phone she grabbed from the house, the girl tipped authorities off to a gruesome scene.

Children were chained to their beds

When authorities arrived at the 4-bedroom house in Perris, they found some of the children shackled with chains and padlocks, the sheriff’s department said.

Conditions inside the house were filthy, as were the siblings. They “appeared malnourished and very dirty,” authorities said.

The 13 siblings ranged from 2 to 29 years old — but the seven adults were so emaciated that they looked like children.

The parents have been charged

David and Louise Turpin are charged with torture and child endangerment. Bail was set at $9 million for each.

The children were apparently home-schooled

The father, David Turpin, ran a private school out of his home called Sandcastle Day School, according to the California Department of Education. Turpin is listed as both the administrator and principal.

They looked happy in vacation photos

Perhaps the oddest juxtaposition in this case is the beaming family photos contrasted with the apparent horror of their home life.

One photo, taken at the parents’ wedding vow renewal in Las Vegas, showed a dozen beaming siblings and a baby, with all the boys wearing identical suits and the girls in matching dresses.

It was not immediately clear if the suspects had attorneys. They have a court hearing scheduled for Thursday.

David Turpin’s mother, Betty, said she doesn’t have any information about the case.

But she said “we feel like one side of the story has been reported. This is a highly respectable family.”

For example, the siblings wore identical outfits based on gender to help “keep up with the kids” during outings, she said.

And when the family went out, the couple would line the children up according to age, and the parents took their positions at the front and back of the line.

Whether other children went to the home school

The Sandcastle Day School is listed as a K-12 private school. It was not immediately clear whether anyone outside the Turpin family was educated there.