Family theories and siblings of people with intellectual and developmental disabilities

Family theories have been used in intellectual and developmental disability (IDD) research as a legitimizing tool for focusing on non-disabled siblings. Although there is value in understanding siblings’ outcomes, family theories have utility beyond this narrow scope. This chapter will draw on social learning theory, embedded family systems theories, the Double ABCX model, lifespan and developmental perspectives, and post-structuralist perspectives, to examine how these theories can be used to understand siblings’ experiences, family relationships, and outcomes. For example, these theoretical ideas enable us to further our understanding of the wider and more interactive factors related to siblings’ psychological, social, familial, community, and societal outcomes, as well as relationships. These theories highlight the need for analyses that include the whole family system and that move beyond simple main effects to include interacting factors, and beyond unidirectional effects to bidirectional effects. Clarifying a broad array of factors that may explain sibling outcomes may help us to consider what covariates to include in statistical models. This chapter will also consider how family theories can help us to consider methodological and epistemological challenges related to sibling IDD research. For example, although these family theories are often described as dynamic, the transient and heuristic nature of capturing any perspective—about a theory, model, or from a research participant—ultimately reinforces how vast and unknowable individual and family experiences are. These family theories also have utility as a self-reflexive tool to consider researcher positionality. Family systems perspectives emphasize the insider-outsider boundary in family systems. Researchers must navigate, respect, and ultimately accept this boundary when researching families and siblings that are not their own.