42-year-old Steven Walter Pladl and his biological daughter Katie Rose Pladl, 20, were both arrested last week after Steven's estranged wife told law enforcement that he impregnated their daughter.
According to police documents, Katie was adopted after she was born. When she turned 18, she used social media to find her biological parents, KRON 4 reports.
Steven's estranged wife, and Katie's mother, told police that she learnt of the pregnancy while reading one of her other children's journals.
According to police, Steven had asked his two younger children to refer to Katie as their step-mother, even though she was her sibling.
After learning about the pregnancy, the wife said she contacted her estranged husband and asked if he had impregnated Katie. He allegedly admitted the baby was his and said they planned to get married.
Both Katie and Steven were being held in the Wake County Detention Centre. They have been charged with incest with adult, adultery, contributing to delinquency.
Steven and Katie were each issued a $1million bond. Steven bonded out of jail, but Katie remains behind bars.