Family background has been shown to be a strong determinant of educational attainment, yet relatively little is known about the role that family background plays in PhD attainment or in the selection into academic careers. In this study, we estimate sibling correlations from Finnish full population register data to comprehensively assess the importance of family background in selection into academia. Our results show that family background accounts for over a third of the overall variation in becoming a PhD and subsequently an academic — a share which is up to four times as large as implied by conventional comparisons by parental education. However, we did not find evidence that family background would be an exceptionally strong determinant of doctoral outcomes when compared to other educational outcomes. Our findings further suggest that sibling similarities in PhD attainment and academic careers may largely be attributed to sibling similarities in prior educational achievement rather than to other family background characteristics.