Brandt is charged with raping his three adopted sons, ages 9, 10 and 12, and prostituting one of the sons to adult males. He also has a 9-year-old adopted daughter.
All four children were from Texas and one adoption was not yet finalized.
In addition to criminal charges, authorities are also examining Brandt's history as a foster parent.
"It has also been brought to our attention from past experiences with Kenneth that he has been bringing children from Texas to Troy as supposed foster children," Troy Detective Chris Tilley wrote in the search warrant affidavit. Brandt was arrested Friday.
A 10-year-old boy shook when asked about being prostituted to two other men by an adoptive father who regularly had sex with him, according to police, who said the boy was fearful of talking because he didn't want to be taken from his home or separated from his new siblings.
The adoptive father, Kenneth Brandt, 39, of Troy, has been charged with raping three boys in his care and compelling prostitution by hiring the 10-year-old out for sex. He and two other men remained in jail Thursday on rape charges.
Federal and local law enforcement officials said they're widening the investigation into child sexual exploitation allegations against the father, who worked out of his home as an insurance claims adjuster.
Troy police said they impounded the father's truck and seized four laptops from the home and a video camera and two wooden paddles from the master bedroom.
An undercover detective in Franklin County, part of a state task force, talked online with the adoptive father, who said he would arrange sex with a 10-year-old boy, Troy police said. He had been led to the adoptive father by another man who had posted a Craigslist ad wanting "taboo" sex, police said.
The adoptive father was going to meet the undercover detective at a McDonald's in a nearby city, but police moved in two days before the scheduled meeting, according to records. They confronted the man with text messages and online communications about arranging sex with the boy, police said in a case report filed in court.