Looks like you found another one, Blam.
"....The wars between the xiongnu "Han" kingdom and Jie, and the downfall of West Jin caused the southward migration of the Han tribe. And this was thought to be the first major maigration of Hakka (Lo Hsiang Lin). Jie ½~ tribe have high nose bridge and deep eye sockets, easily recognized. When Shi Le's nephew became the emperor, a Han general Ran Min ¥T ¶{ overthrew Hou Zhao and slaughtered all people with high nose bridge. This indicates an extreme ethnic conflict existed between the Han and non-Han at that time, close to the ethnic cleansing we see today in Bosnia.
It is likely that to avoid genocide, some Xiongnu disguised as Han and move to the south with the Han. Many Han aristocrats also had hundreds to thousands of Xiongnu servants and soldiers. However, Jin dynasty is a period with highly distinct class difference. It is difficult for someone with a clearly distinct physical feature to infiltrate Han even as a civilian unless there was some inter-ethnic marriage or affiliation with the Han aristocrats. It was almost impossible for a xiongnu to become a nobility among Han. The number of Xiongnu who could mingle with Han and fled to the south could not be in great number. Culturally speaking, although Liu Yuan was totally Sinicized (Hanized), most of the Xiongnu inhabitants in central China could not have received the kind of education. It would be quite amazing if the Xiongnu decendents could upbring so many famous names like Han YuÁú ·U , Wang YangMing ¤ý ¶§ ©ú , Zhu Xi¦¶ ¿Q ...."