What is the Family?:
Everyone is or has been part of a family, but defining the boundaries of a family is difficult to do. In modern America, family is used almost exclusively in reference to the nuclear family of a father, mother, and their biological children. In the Bible, however, family has much broader overtones. In the Bible, the family might include as little as the household, but it might further refer to a clan or tribe even an entire nation.
Family and the Household:
In the New Testament, the usual word for family is oikia, which means house or household. Therefore at the very least, the New Testament family includes everyone who lives in a house this would include not just blood relatives, but also slaves and servants. In Christianity, the oikia was further broadened to include the church community as well: a church is the household of God. Familial relationships are thus models for spiritual relationships.
Family & Marriage:
The most obvious way that a family expands is through the birth of new members. Perhaps more important, however, is the act of marriage. Through a marriage ritual, not only do two otherwise unrelated people become family, but two families become related as well. Marriage creates important social and familial bonds which, in turn, are part of the basis for society itself.