Amnon was the oldest son of King David and his wife, Ahinoam. His story was told in 2 Samuel 13.
2 Samuel 13
After his father had sinned by killing Uriah the Hittie for his wife, Amnon developed lustful feelings towards his half-sister, Tamar, which was of course, forbidden by Hebrew law. His lustful feelings towards his younger sister were so powerful, that he went to his cousin, Jonadab, for advice. Jonadab suggested to him that he should lure Tamar to his quarters by pretending to be sick and that he should also make a request to her that involved a special meal. Amnon does as his cousin had advised, and he proceeded to rape his sister, and then threw her out of the house. Absalom, Amnon's half-brother, discovered what his brother had done to his half-sister, and he killed him when he was drunken out of his mind.