2 Samuel 13:1-3

And it came to pass after this, that Absalom the son of David had a fair sister, whose name was Tamar; and Amnon the son of David loved her.

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.

But Amnon had a friend, whose name was Jonadab, the son of Shimeah David’s brother: and Jonadab was a very subtil man.