2 Samuel 13:2, 4

Amnon became so obsessed with his sister Tamar that he made himself ill. She was a virgin, and it seemed impossible for him to do anything to her.

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.”