Samuel Stokes pleaded guilty Wednesday to one count each of conspiracy and conflict of interest. He is a former House employee and Perzel's brother-in-law.
Former Perzel campaign aide Don McClintock also pleaded guilty to one count of conspiracy.
Both men appeared before Dauphin County Judge Richard Lewis in Harrisburg. They must cooperate in the prosecution of seven other GOP defendants under an agreement with the state attorney general's office.
Those defendants include Perzel, a Philadelphia resident, and another former high-ranking state representative, Brett Feese of Lycoming County.
Paul Towhey, one of two former Perzel chiefs of staff, is slated to enter a guilty plea Friday.