The family nucleus is considered:
1. the husband and wife without children;
2. the husband and wife having unmarried children;
3. one of the parents having unmarried children.
[p. 34]
All the children who are not married living together with the parents (regardless of if they are coming from a legal marriage or not, from prior marriage of one of the partners or whether they are adopted children) are considered as part of the family nucleus.
The children who were married but at the reference moment of the census were divorced or widowed, and who returned to the parent's household under the conditions that they do not have children of their own on subsistence are also considered as part of the family nucleus.