sorrow

周本纪：
古公有长子曰太伯，次曰虞仲。太姜生少子季历，季历娶太任，皆贤妇人，生昌，有圣瑞。公曰：“我世当有舆者，其在昌乎？”长子太伯，虞仲知古公欲立季历以传昌，乃二人亡如荆蛮，文身断发，以让季历。

It's a story in ancient Chinese history. The emperor has three sons among whom the youngest son had the smartest kid Chang. One day the emperor asked, "who do u think should take over my regime? Should he be Chang?" The two elder sons understand that their father tends to hand over his power to their younger brother so that his brilliant grandson could surely be the next king after his father. Therefore, these two elder brothers leave the palace for uncivilized place, make themselves tattoo like guilty people, cut their hair which presents their connection with their parents, to secure the throne for their younger brother, and their smart nephew.

Why is it so sad.