Decreasing trends in birth rates in developed countries during the past decades, which threaten the sustainability of their populations, raise concerns in the areas of employment and social security, among others. A decrease in willingness to bear children has been examined in the international literature from several (biological, socio-cultural, economic, and spatial, etc.) aspects. Among these, the question of the effectiveness of fiscal incentives has been raised, with arguments that these are positive, but not significant, to birth rates; our study also concludes this. In Hungary, from 2010 onwards, the government has introduced very high tax allowances for families and, from 2015, has provided direct subsidies for housing purposes, all within a framework of a new family policy regime. This paper presents an evaluation of family policy interventions (e.g., housing support, tax allowances, other child-raising benefits), with the conclusion that fiscal incentives cannot be effective by themselves; a sustainable level of birth rates can only be maintained, but not necessarily increased, with an optimal design of family policy incentives. By studying the Hungarian example of pro-birth policies there is shown to be a policy gap in housing subsidies.