Brandon and Viviana Gunn were arrested Saturday, KIRO-TV reported. A day earlier, police had discovered Brandon Gunn's 15-year-old brother sleeping in a Bremerton, Wash., park.
Investigators say the teen told police his brother and sister-in-law hung him by his hands from a beam, and beaten, burned and tortured him with staples. He said he spent days locked in the dog crate.
The teen said he escaped by somehow getting duct tape off his mouth and then used his teeth to get the tape off his wrists.
Neighbors said police searched the Gunns' house near Silverdale.
"We heard crying but I assumed it was the younger child off and on over there, " Janet Ladyman, a next-door neighbor, told KIRO.
Police said the boy, who is now in protective custody, was apparently afraid to go to authorities after he escaped.
The Gunns were being held in Kitsap County Jail on $500,000 bail each.