Harry Potter and the Half-Blood Prince
Dumbledore gives private lessons to Harry. They usually involve looking into a Pensieve, which holds old memories. In flashback, Harry learns that Voldemort was the product of an unhappy witch and a Muggle father that never loved him. The witch was named Merope and she had an older brother and father that were very bad to her. They made her work and crushed her spirit. A Ministry of Magic wizard came and arrested the father and brother. Merope left the house and gave a love potion to a young man she liked named Tom Riddle.