The 13 California siblings who police say were starved and chained to beds by their parents rarely left their dishevelled house and, when they did, appeared small and pale and acted strangely, neighbours say.
David Allen Turpin, 57, and Louise Anna Turpin, 49, were arrested on Sunday (local time) and each charged with nine counts of torture and 10 counts of child endangerment after a 17-year-old, emaciated girl escaped the house in Perris, east of Los Angeles and called police, the Riverside County Sheriff's Office said.
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?" Ms 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."
Two years ago, while walking around the neighbourhood admiring Christmas lights and decorations, Ms 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 US$9 million (NZ$12.37 million) bail each, police said.
Six of the couple's children are minors, while the other seven are over 18, parents said.