Data were collected from 708 adult children nested within 274 later-life families from the Within-Family Differences Study to explore the role of perceived maternal favoritism in the quality of sibling relations in midlife. Mixed-model analyses revealed that regardless of which sibling was favored, perceptions of current favoritism and recollections of favoritism in childhood reduced closeness among siblings. Recollections of maternal favoritism in childhood were more important than perceptions of current favoritism in predicting tension among adult siblings, regardless of age. Taken together, the findings from this investigation are consistent with childhood studies showing that siblings have better relationships when they believe that they are treated equitably by their parents.