2 Samuel 13:3-4

Now Amnon had an adviser named Jonadab son of Shimeah, David’s brother. Jonadab was a very shrewd man. He asked Amnon, “Why do you, the king’s son, look so haggard morning after morning? Won’t you tell me?” Amnon said to him, “I’m in love with Tamar, my brother Absalom’s sister.”