This paper examines empirically the impact of reproductive externalities on fertility behaviour in one developing society - Kenya. We examine this issue by quantifying the effects of group membership on the number of children ever born. The focus of this study is the identification of structural forms of social interaction operating across individuals in the context of fertilty behaviour. Although a number of commentators are careful to point out the conditions under which structural forms of dependence may be separated from residual dependence, we also highlight the importance of different expressions of structural dependence. Thus, although in the majority of empirical applications which include social interactions, a single mode of social interaction is assumed, following the typology suggested by Glaeser, we consider a model which includes multiple expressions of social interaction. If the assumption of a single model of interaction is made, erroneously, then it is possible to arrive at incorrect inference