呉県
Lu Kang was from Wu County, Wu Commandery, which is in present-day Suzhou, Jiangsu. His grandfather, Lu Xu (), served as a minor officer in a commandery in the early Eastern Han dynasty. When the prince Liu Ying plotted to overthrow Emperor Ming, Lu Xu was implicated, arrested and tortured. Emperor Ming eventually pardoned Lu Xu but placed him under permanent house arrest. Lu Xu died of old age. Lu Kang's father, Lu Bao (), had a reputation for his morally upright character. The Han government repeatedly asked Lu Bao to join the civil service but he refused.