I spotted the same thing, and there's never a source given. Allegedly his great-great-great-great-great-great-great-great-great-great-great-great-great-great-great-grandfather (or 15th great-grandfather for short) was totally Han, the son of the scourge of the Xiongnu - https://en.wikipedia.org/wiki/Li_Guang
A timely reminder that, damn, China is olllldddd.