Historically speaking, people with surname Wei are the descendents of imperial clan.
Dating back to Western Zhou Dynasty, after conquering the Shang Dynasty (which was also known as Yin Dynasty), King Wu began to enfeoff his brothers generously. Granted with the capital of Shang Dynasty and its surrounding places as well as seven clans of the conquered Shang Dynasty, Kang Shu, brother of King Wu founded the State of Wei with its capital in Chaoge (today's Qi county in central China's Henan province). From then on, offspring of Wei imperial family took the title of their nation Wei as their surname. In that sense, Kang Shu was the ancestor of surname Wei.
However, State Wei moved its capital several times after being defeated by other States, and became weaker and weaker. It was later destroyed by States of Qin and Wei in Warring States period. Although the State was wiped out, descendents of Wei lived and multiplied peacefully up to modern times.
Apart from that, the change of surname by other ethnic minorities also constituted the enlargement of surname Wei. During Northern and Southern Dynasties, a nomadic tribe Xianbei entered the central plain and some of Xianbei minority took surname Wei during their adoption of Han civilization.
Although the surname is not so popular with Chinese, there is no lack of celebrities with surname Wei throughout the history, such as calligrapher Wei Heng who was regarded as the master of cursive script, Zhang script, Li script (an ancient style of calligraphy current in Han Dynasty) as well as San script in Western Jin Dynasty. He also wrote a book commenting on the four styles of scripts. Astronomer and mathematician Wei Pu who was blind since childhood was popular in Northern Song Dynasty (960-1271A.D.)for compiling Fengyuan Calendar.
By People's Daily Online