Complex sentence: Con was a student who was influential to others, Nick and Effie's cousin, left Hartley to go in USA in episode 71, romantically involved with Katerina Ioannou.
Split into simpler sentences: Con was a student who was influential to others,; he was Nick and Effie's cousin. He left Hartley to go to the United States in episode 71, romantically involved with Katerina Ioannou.