Final answer:
Yusuf's brothers were jealous of him because he was their father's favorite and because he had prophetic dreams that implied he would become more powerful than them in the future.
Step-by-step explanation:
The brothers of Yusuf (Joseph) were jealous of him because he was their father's favorite and because he had prophetic dreams that implied he would become more powerful than them in the future. This jealousy led them to plot against him and eventually sell him into slavery.
One example of Yusuf's prophetic dreams is when he dreamt that the sun, moon, and eleven stars were prostrating to him. This dream angered his brothers even more.
The brothers' jealousy can be seen in the story of Yusuf in the Quran, specifically in Surah Yusuf (Chapter 12).