Population and demographic studies have made a major contribution to the study of children and childhood. However, the demographic analysis on children has rarely been carried out using the children as the unit of analysis; the usual unit is the household, the family or the mother. For example, standard demographic measures of fertility are women-based and, therefore, do not entirely reveal the size of a child’s family of orientation. Children are considered as related to their parents but not to other siblings or even other relatives. The purpose of this article is to use three child-based measures to analyse demographic data from a child’s perspective: namely, children’s mean family size, net mean family size and the mean number of children that co-reside with other children. These three measures are applied to data from the 1998 Census of Cambodia. The argument proposed in this article is that the study of children is incomplete unless they are also studied as unit of analysis in their own right and with respect to other children and not only to adults. It is demonstrated that, in fact, this approach may open new avenues to the study of children from a social perspective.