The long-lasting fertility decline and the lowest-low fertility level have strongly affected family size in Italy. From 1961 to 2011, the average number of individuals per household moved from 3.6 to 2.4, and the proportion of households with 6 members or more from 14.4% to 1.4%. Consequently, a question arises: what are the conditions to build a large family (4 or more children) – a very special minority – in a context of lowest-low fertility? Literature is scarce, and sample surveys are not appropriate to study this topic, because of the low number of cases. Accessing to individual micro-data of the 2011 Italian census, we are interested in analyzing some structural characteristics of large families which could shed light on the factors that are on the basis of their formation. What are the roles of income/social class or female education? Are there still cultural bases? The traditional fertility differences among Italian regions have recently disappeared, but what about numerous families? Could some family changes related to SDT have any effect on the formation of such families? In what extent large families of foreign population – that in the last decade have registered a significant increase – are differently characterized from native population? Results from logistic models conducted separately on native and foreign residents suggest that large families, although a minority, find room in contexts which are more heterogeneous than we could think, especially among autochthonous inhabitants.