A second man charged in the slayings has pleaded not guilty and could face the death penalty if convicted.
Trevin Sanders, 19, pleaded guilty to aggravated murder and other charges Thursday in Mercer County, north of Dayton, as part of an agreement with prosecutors. His sentencing is scheduled for April 15, and he faces up to life without parole.
Colleen Grube, 47, and her father, 70-year-old Robert Grube, were found dead in November 2011 by a relative in the ransacked home on a lonely country road surrounded by farm fields outside the village of Fort Recovery.
The farmhouse slayings stunned residents in the rural communities of west-central Ohio where violent crimes are rare. In the days afterward, parents wouldn't allow their children to be dropped off at empty homes after school and neighbors were asked to look out for one another.
Sanders, who had been in prison in Indiana since October 2012 on unrelated theft charges, and 23-year-old Bryant Rhoades were charged last March in the slayings. Rhoades has pleaded not guilty to aggravated murder and other charges.
Both are from Union City, a town that straddles Indiana and Ohio.
Mercer County prosecutor Matt Fox said in court Thursday that Sanders said he shot Colleen Grube several times and that Rhoades then shot the woman's father, who was found in his wheelchair.
"They were killed to prevent a group of subjects from being identified," Fox said, according to The (Celina) Daily Standard.
Messages seeking comment were left with Rhoades' attorneys on Friday.
Investigators said the big break came in January 2012 when Indiana authorities contacted a sheriff's department in Ohio and said they made an arrest in an unrelated case and were curious whether there was a connection to the farmhouse slayings.
Colleen Grube's sister-in-law found the bodies after she didn't show up to babysit her niece. She said she found Robert Grube dead in his wheelchair and his daughter's body on a couch.