In chapters 2 & 3 of the Politica, Althusius identifies the family as the basis of human society. Of course, this is sort of a common place. We hear this sort of thing in political rhetoric all the time today. It was an old concept (indeed a biblical one) even in Althusius' day, but it was not popular. The nation state was emerging with its strong centralized power. Althusius believed that society and government was organized around consent and commitment, that is, covenants. There was no absolute human authority.
Are these two ideas compatible? Can the basis of society be the family and, at the same time, consent? After all, we do not general choose our family members. But a moments reflexion identifies the basis of the family is the covenant between man and wife. If were but one society, only one family, at its base would be a commitment between a man and his wife, between a woman and her husband. This is the teaching of the Bible. Adam and Eve were joined together in marriage by God (see Genesis 2, and Matthew 19). In fact the creation of man included the creation of both male and female, they together complete the concept of man.
The bond of this union is such that it even trumps the duty of a child to his or her parents (see again the two references above). Now the law of God does not pit one duty against another, we are to honor father and mother AND keep the marriage bond pure and unbroken. However, we live in a sin-sick world and their are times when our duty to God overrules our duty to our neighbor. It is better to obey God rather than men, says our apostles. When we remember that our duty to respect and honor civil government is derived from the fifth commandment (our duty to honor our parents), the sacredness and solemnity of the marriage bond is intensified. In human society it is covenant, not power, that is fundamental.
But can the same argument be made outside of revelation? I think so. While our understanding of humanity's early years is clouded and based largely on conjecture, recorded history sees mankind already organized in complex societies. And common to all those societies is the institution of marriage in one form or another. It is true, that hierarchies of power asserted themselves over the mutual commitments of men, patriarchs of families began to undermine their sons' marriages by demanding unwavering loyalty, and that sacred institution became a way of extending political clout, it became one more tool of power. But in the beginning it was not so, and our Lord makes that clear. What God has joined together, let no man put asunder.