2 Samuel 13:1-4

1It happened afterwards that Absalom the son of David had a beautiful sister whose name was Tamar, and Amnon [her half brother] the son of David was in love with her.

2Amnon was so frustrated because of his [half-] sister Tamar that he made himself sick, for she was a virgin, and Amnon thought it impossible for him to do anything to her.

3But Amnon had a friend whose name was Jonadab the son of Shimeah, David’s brother; and Jonadab was a very shrewd (cunning) man.

4He said to Amnon, “Why are you, the king’s son, so depressed morning after morning? Will you not tell me?” And Amnon said to him, “I am in love with Tamar, my [half-] brother Absalom’s sister.”