Manuel Perez, age 47, has been in a Sacramento County jail since December on charges of committing lewd acts with two minor females more than a decade ago.
The Sacramento County Sheriff's Department says he hired someone to kill one of the two women who accused him.
The department says his 45-year-old sister, Natalia Perez, is suspected of giving the intended killer a photograph of the victim and a vehicle as payment.
They are being held without bail on suspicion of solicitation to commit murder and criminal conspiracy. It was unclear if they had attorneys.
Deputies are also seeking a second woman.