Jeffrey S. Sandusky, the 41-year-old son of convicted child-sex abuser Jerry Sandusky, pleaded guilty Friday in Centre County to attempting to persuade two teenage sisters into sexual acts.

The younger Sandusky, who worked as a corrections officer at Rockview State Correctional Institution in Bellefonte, was facing a trial this month when he agreed to the plea deal, which requires him to serve at least three to six years in state prison. Prosecutors said they will seek a sentence of four to eight years. His sentencing is scheduled for Dec. 8.

Sandusky, one of six children adopted by the former Pennsylvania State University assistant football coach, was charged with soliciting naked photos from a 16-year-old girl in 2016. In 2013, officials said, he asked the girl's older sister for oral sex. That victim was 15 at the time.

The girls were the daughters of Sandusky's then-live-in girlfriend.

Pennsylvania State Police launched an investigation after the father of the younger girl discovered text exchanges from Sandusky asking for naked photos.

"While we were fully prepared to proceed to trial, today's guilty plea to all charges ensures a significant prison sentence for defendant's solicitation of child-sex crimes with two minors that once completely trusted him," said Centre County District Attorney Stacy Parks Miller in a statement.

"This outcome also ensures the victims need not suffer the trauma and re-victimization of testifying at trial, and, importantly, the defendant will have to comply with strict sex-offender registration requirements for the remainder of his life. We are happy that these girls can move forward and experience a life with adults that deserve their trust," Parks Miller said.

Jerry Sandusky is serving a 30- to 60-year sentence in state prison after being found guilty in 2012 of sexually abusing 10 boys.