This article examines the issue of siblinghood in older age. The author starts by referring to sociological studies criticising the a-theoricity of empirical research in this field. She proceeds to analyse the most influential theoretical approaches used to study relationships between parents and their adult children (i.e. the theory of intergenerational solidarity and the theory/ concept of intergenerational ambivalence) and to critically assess their potential to serve as a guideline for empirical research on siblinghood and provide a framework for interpreting research findings on intragenerational/sibling relationships. The article devotes more space to the concept of ambivalence, which, the author argues, is a more appropriate approach for exploring relationships between older siblings. It also presents a basic overview of the state of empirical knowledge on adult siblinghood.