Manuscript type: Research paper Research aims: This paper investigates how family ownership affects firm's earnings quality. The focus is on firms listed on the Korean Stock Exchange (KSE). Design/Methodology/Approach: This study uses panel data to classify family ownership into two categories: pure family ownership and ownership-control disparity (wedge) where wedge is further divided into 1) wedge ratio and 2) wedge multiplier. In addressing the category of ownership-control disparity, it is important to measure how much control rights are greater than ownership rights. Therefore, this study employs the wedge multiplier to overcome the limitation of not separating management control and ownership. Firms' earnings quality is tested by using four proxies proposed by Jonas and Blanchet (2000): 1) persistence, 2) value relevance, 3) conservatism, and 4) accruals quality. Research findings: This research finds family ownership to be positively associated with earnings quality, value-relevance and accruals quality. However, ownership-control disparity does not reduce the earnings quality. This finding is not consistent with previous studies. Thus, it is deduced that the controlling family shareholders of the chaebol firms have a dominant influence on firms which they invested in by using affiliated ownership. Significant ownership-control disparity is prevalent in chaebol firms, resulting in low earnings quality.