2 Samuel 13:2, 4

Amnon was so frustrated because of his sister Tamar that he made himself ill, for she was a virgin, and it seemed hard to Amnon to do anything to her.

He said to him, “O son of the king, why are you so depressed morning after morning? Will you not tell me?” Then Amnon said to him, “I am in love with Tamar, the sister of my brother Absalom.”