We investigated the associations among marital relationship quality, mothers' parenting styles, and young children's sibling relationship quality drawing on the principles of family systems theory. Survey data were collected from 130 mothers who had a target child (mean age = 4.6 years) with a sibling close in age. The sample consisted of participants who self-identified as Mexican-American (49%), European-American (20%), and Taiwanese in Taiwan (24%). Structural equation modeling was used to test the direct and indirect effects of marital relationships on children's sibling relationship quality through parenting styles and the reciprocal association between sibling relationship quality and parenting styles. The findings revealed evidence of a direct effect of marital relationships on sibling relationship quality and bidirectional relations between sibling relationships and parenting styles. The importance of research on bidirectional associations between sibling relations and parenting styles is discussed.