A family member of an EU citizen and other relatives comparable to a family member are defined in section 154 in the Foreign Nationals Act.
In practice, a family member of an EU citizen refers to:
spouse of an EU citizen,
an EU citizen’s or their spouse’s children under the age of 21,
Dependent children, grandchildren or other relatives in the descending line of an EU citizen or their spouse,
dependent parents, grandparents or other relatives in the ascending line of an EU citizen or their spouse and
provider of an EU citizen under the age of 18 residing in a member state.
A registered partnership is comparable to marriage. Persons living in a marriage-like relationship and sharing the same household are comparable to a married couple regardless of their sex, provided that they have lived together for at least two years. This is not required if the persons have a child in their joint custody or if there are other compelling reasons.