European Union: more single households, fewer familiers. What geography? What are the explanatory factors?

Households, i.e. all the individuals living within one dwelling, are the basic geographical unit of socialization. Falling fertility rates, leading to smaller families, and ageing populations, resulting in a higher proportion of (small) elderly households, have led to a decline in average household size in the EU27. However, despite the fact that this demographic trend is common to all EU27 countries, household and family characteristics are not uniform across all Member States: other factors play a decisive role and potentially significant differences persist. These contribute to a highly diversified European Union, but a geographical typology is nonetheless possible. What is this typology? What factors explain it?