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BELLEFONTE, Pa. — A son of former Penn State assistant football coach Jerry Sandusky, serving decades for child molestation, was himself sentenced to prison Friday on child sexual abuse charges.

Jeffrey Sandusky was sentenced to 3½ to 6 years in prison after pleading guilty to pressuring a teenage girl to send him naked photos and asking her teen sister to perform a sex act.

Jeffrey Sandusky, 42, pleaded guilty on the eve of his trial in September to 14 counts, charges that included solicitation of statutory sexual assault and solicitation of involuntary deviate sexual intercourse.

This undated file photo provided by the Centre County Correctional Facility shows Jeffrey Sandusky. Jeffrey Sandusky, the son of former Penn State University assistant coach Jerry Sandusky has pleaded guilty pressuring a teenage girl to send him naked photos and asking her teen sister to give him oral sex, Friday, Sept. 15, 2017. Centre County Correctional Facility / AP file

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The Centre Daily Times reported Jeffrey Sandusky's attorney said there was never any physical contact between his client and the victims.

Authorities said he knew the girls through their mother, and that a year ago their father turned over incriminating text messages sent by Jeffrey Sandusky.

A court affidavit said Jeffrey Sandusky told the girl he pressured for photos last year that "it's not weird because he studied medicine." He directed her "to not show these texts to anyone," police said.

Related: Sandusky Case Bombshell: Did 6 Penn State Coaches Witness Abuse?

Jeffrey Sandusky is one of the six children adopted by Jerry and Dottie Sandusky and has been a stalwart supporter of his father, often attending court proceedings.

He will be on probation for a year after release.

Jerry Sandusky is serving 30 to 60 years in prison for sexually abusing 10 boys.

He maintains his innocence but recently lost an attempt to have charges thrown out or a new trial under the state's Post Conviction Relief Act.

The Corrections Department said Friday that Jeffrey Sandusky was fired as a Rockview State Prison guard late last month. He had been with the agency since August 2015.