A couple was convicted Friday of sexually abusing their young son, who testified he had frequent sexual encounters with his mom while his dad offered him instructions or tips on what to do. The 14-year-old boy told jurors at his parents' sex abuse trial that he began having intercourse with his mom on his eighth birthday, about a year after his dad began showing him pornography. The northeastern Pennsylvania boy, who was home-schooled, said he didn't know that sex with his mom was wrong until years later, when he was placed in foster care.