Mikael Shane Pruett was arrested last summer after his victim was discovered to be 32 weeks pregnant.
The child complained of stomach cramps, but upon examination learned that she was expecting a child.
Opening up about the news, the young girl said: "I didn't know what pregnant felt like, so I didn't know."
The children's grandfather attempted to conceal his crimes by concocting a story about a 14-year-old boy who had relations with his granddaughter at a country fair.
The story was soon discovered to be false however when the victim's due date didn't match the timeline of events presented by her grandfather.
Apologising during his trial, Mr. Pruett was told he 'lacked any semblance of a conscience' by the presiding judge.
The grandfather, who has a history of lewd conduct was the girls' legal guardian, and will only be eligible for parole should he live to see his 105th birthday.
