In the sixth book, "Harry Potter and the Half-Blood Prince" Harry enters a tumultuous puberty that, Rowling says, is based on her and her younger sister's own difficult teenage years. Rowling also made an intimate statement about Harry's personal life: "Because of the demands of the adventure that Harry is following, he has had less sexual experience than boys of his age might have had". This inexperience with romance was a factor in Harry's failed relationship with Cho Chang. Now his thoughts concern Ginny Weasley, Ron's sister, a vital plot point in the last chapter when Harry ends their budding romance to protect her from Voldemort.