2 Samuel 13:2, 4

And Amnon was so vexed, that he fell sick for his sister Tamar; for she was a virgin; and Amnon thought it hard for him to do any thing to her.

And he said unto him, Why art thou, being the king's son, lean from day to day? wilt thou not tell me? And Amnon said unto him, I love Tamar, my brother Absalom's sister.