While the decrease in family sizes is mostly associated with the first demographic transition, the Second Demographic Transition is mainly associated with an increase in childlessness. However, parity-specific analyses show that during the recent fertility decline both processes can be observed. Recent decomposition analyses (Bujard/Sulak 2016) even reveal that, at least in Germany and the UK, the decrease of higher order births has a stronger effect on the decline of cohort fertility than the increase in childlessness. From a theoretical perspective, this is remarkable because the Second Demographic Transition is expected to go along with increasing diversity of family forms, as an expression of individual self-realisation and weakening norms. Instead, empirical research reveals an increasing standardisation of family sizes and a two-child-norm that is well-established throughout Europe and presumably linked to the change in fertility. This paper investigates empirically and debates theoretically the reasons for these findings. Our, partly quantitative partly qualitative, content analyses of newspaper archives from the 1950s and 1960s in Germany and the UK reveal a number of public debates that take critical standpoints against large families. The most outstanding debate is the severe anxiety of overpopulation threatening the survival of mankind, referred to as the “population bomb” (already several years before Paul Ehrlich’s book). This debate and others start to peak in the years before the start of fertility decline in Europe. This suggests that fear of overpopulation in the early 1960s has resulted in the social construction of a two-child-norm and an intensified discrimination of large families, according to which three or more children indicate an undisciplined and irresponsible generative behaviour, inadequate for people in modern societies.