Scholars of social mobility increasingly study the role of family background in shaping attainment throughout the entire life course. However, research has yet to establish whether the family characteristics influencing early career attainment are the same as those influencing late career attainment. In this research note, I apply an extended sibling correlation approach to analyze brothers’ life cycle earnings and family income, using data from the U.S. National Longitudinal Survey of Youth 1979. My analysis reveals a near-perfect correlation in the family characteristics that affect attainment at early, mid, and late career stages. This finding has significant implications for how mobility scholars conceptualize the impact of family background across a career. It suggests that family background forms a single, consistent dimension in determining attainment throughout the life course. Further analysis also indicates that the imperfect relationship between current and lifetime income is exclusively driven by within-family processes.