The oldest of the three sisters was just 17 years old.
The girls were allegedly held captive in the bedrooms of their US home in Tucson, Arizona, for two years. They alleged they did not have a wash for four to six months.
The sisters were rescued on Tuesday and the mother Sophia and stepfather Fernando Richter were arrested on kidnapping and child abuse charges. The 34-year-old man also faces one count of sexual abuse with a person under 15.
Their case came to light when two of the girls ran to a neighbour's home for help after the stepfather allegedly threatened them with a knife.
The two younger girls are aged 12 and 13.
The sisters were found to be malnourished and filthy. The younger girls and their sister had not seen each other for nearly two years, police said.
The home was a house of horrors with 24-hour surveillance, an elaborate alarm system and music blasted round the clock, police said.
The girls resorted to using their closets as modified bathrooms when their parents failed to let them out, the New York Daily News reported.