12 The rights here spoken of, belonging to each individual man, are seen in much stronger light when considered in relation to man's social and domestic obligations. In choosing a state of life, it is indisputable that all are at full liberty to follow the counsel of Jesus Christ as to observing virginity, or to bind themselves by the marriage tie. No human law can abolish the natural and original right of marriage, nor in any way limit the chief and principal purpose of marriage ordained by God's authority from the beginning: "Increase and multiply."(3) Hence we have the family, the "society" of a man's house - a society very small, one must admit, but none the less a true society, and one older than any State. Consequently, it has rights and duties peculiar to itself which are quite independent of the State.
Source: Rerum Novarum (Vatican.va)