Amnon was the first born son of David. His mother was Ahinoam from Jezreel  and he was born in Hebron while his father was still fighting the House of Saul and before David became King of all of Israel. His story is told in the Old Testament of the Bible in the Book of II Samuel.
When Amnon was full grown, he developed strong feelings for his half-sister Tamar. He pretended to be ill and asked that she take care of him. David questioned it, but agreed. When they were alone, he forced himself upon her against her will, and then wanted nothing further to do with her. Tamar told her brother Absalom who waited two years until he had the opportunity to get revenge, having his servants kill Amnon while Amnon was drunk with wine and away from his father's house.