The district attorney said the couple chained their children as punishment.
A 17-year-old daughter who climbed out a window on Sunday and called 911 on a cellphone had plotted her escape for two years, he said. Another sibling escaped with her but turned back out of fear.
Hestrin said all 13 victims were severely malnourished and as a result some have cognitive impairment and a lack of basic knowledge. He said a 29-year-old female victim weighed 82 pounds.
The victims were not allowed to shower more than once a year, he said.
In an interview, grandparents of the children said their son's family looked happy and healthy when they last visited California six years ago.
"They were just like any ordinary family," said Betty Turpin, the 81-year-old mother of David Turpin. "And they had such good relationships. I'm not just saying this stuff. These kids, we were amazed. They were 'sweetie' this and 'sweetie' that to each other."
Betty Turpin and her husband, James Turpin, of Princeton, West Virginia visited her son's family for five days at their previous home in Murrieta, California.
Betty Turpin told the Southern California News Group on Wednesday that they were still in shock from learning that her son and his wife were arrested.
Betty Turpin said her son told her he had so many kids because God wanted him to. She said her son shared her Pentecostal Christian faith but he wasn't affiliated with a church in California.
"I feel they were model Christians," she said. "It's hard to believe all of this. Over the years, the Lord knows what happened."
James Turpin said during their visit, "they all looked to me well-adjusted. They weren't skinny or nothing. They were joyous to see us."
He said they were dealing with social workers in attempting to connect with their grandkids, who are hospitalized as they recover from their yearslong ordeal.
On Wednesday, authorities searched the couple's current home in Perris, 60 miles southeast of Los Angeles. Investigators removed dozens of boxes, what appeared to be two safes and pieces of a bed frame.
Some siblings were shackled to furniture in the foul-smelling four-bedroom home that looked perfectly normal from the outside.
The Turpins have lived in two Riverside County communities since moving to California, and police said they were never called to either home, nor were any reports fielded by child protective services.
It's not clear what motivated the Turpins to live a secluded life with their large brood or what went on in the house.
Psychiatrists say that even in cases of extreme deprivation, it's common for feelings of helplessness or confusion to lead to staying in place despite opportunities to flee.
"This happens all the time. The number of individuals who would immediately respond to an opportunity where they could get away is very small compared to the number of people who would have that paralysis and insecurity and confusion about what to do," said Dr. Bruce Perry, a psychiatrist and senior fellow at The ChildTrauma Academy in Houston.
The vulnerable girl might have been shamed, beaten or threatened with violence and only after many missed opportunities did she probably work up the courage to act, Perry said.
"It's pretty remarkable that she'd do that," he said. "The power that must have been exerted to keep an entire family like that for so long must have been pretty sophisticated."