It is now well-established that business groups (BGs) - an inimitable multifirm structure that enables legally distinct firms to take coordinated action - constitute a dominant organizational form in many economies around the world. The BG phenomenon has attracted sustained scholarly attention over the last three decades. Despite the shift in BG research toward BG heterogeneity and strategic performance outcomes, prior reviews and the last meta-analysis a decade ago focus narrowly on the question of whether BGs confer a financial performance advantage on affiliated firms. The authors provide a more extensive account of the BG effect and an in-depth review of the theoretical approaches used in prior work by focusing only on family-controlled business groups (FBGs) - the dominant type of BG. The authors make three contributions. First, they develop a parsimonious organizing framework to summarize extant FBG research in a nuanced way - specifying the relationships examined, theoretical explanations advanced, and empirical evidence adduced. This summary reveals that extant FBG theorizing is predominantly structurally focused. Second, the authors propose a reorientation of FBG research toward a microfoundations-based approach. They develop a scheme for theoretical “taking” and “giving” of relevant microfoundational frameworks from contiguous management subfields to systematically identify potential paths ahead for future FBG theorizing. Finally, the authors granularly discuss illustrative microfoundation-based frameworks, outlining how their application could both enrich and better integrate FBG research with contiguous management subfields such as entrepreneurship, family business, and strategy research. The authors thus consolidate their understanding of FBG research, identify gaps, and suggest promising pathways for future work.