Erzhu Tianguang's father was a cousin of Erzhu Rong, who was a Northern Wei general and the chief of the ethnic Xiongnu Qihu (契胡) tribe.
In 529, Erzhu Tianguang was one of the generals under the command of Erzhu Rong's close associate Yuan Tianmu (元天穆) when Yuan Tianmu attacked and defeated the rebel general Xing Gao (邢杲).