2 Samuel 13:2, 4

And Amnon was so vexed that he fell sick because of his sister Tamar; for she was a virgin; and it seemed hard to Amnon to do anything unto her.

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