Charlie Plex is a Ravenclaw student at Hogwarts. Despite being in a relationship with Cassidy Gamp at the time, he had a sexual relationship with Donna Shacklebolt for several months. She ended it when he revealed his desire to break up with Cassidy and be in a real romantic relationship with her.
The summer before seventh year he met prefect Clancy Goshawk at one of his brother's parties and they began to go out. They broke up, however, when Marlene Price informed Clancy that he had been cheating on her with Shelley Mumps.
All sexual escapades aside, he is shown to still want to be with Donna whilst holding a grudge against her for rejecting him.