Individual differences between families are as varied as are families themselves.
A "family" is "a group of persons related by marriage or blood ties, or even by adoption—and also by the family bond." So, a family may be two adults who are committed to living together and loving each other. A family may include more than two adults; parent(s) living with grown-up child(ren) or siblings or adult siblings or cousins living together. A family may also include children of any number, age, or relationship to any of the adults in the group. All these possible combinations reflect relationships based on marriage, blood ties, or adoption.
A "family" also involves bonding between its members. Family members care for each other, share work and recreation, collaborate to reach common goals for each other as individuals or for the group, help each other to live as part of the community as a whole, and fulfill human needs for love and recognition of self achieved through connection with others.