From Pope St. John Paul II’s Apostolic Exhortation Familiaris Consortio (1981):
In matrimony and in the family a complex of interpersonal relationships is set up—married life, fatherhood and motherhood, filiation and fraternity—through which each human person is introduced into the “human family” and into the “family of God,” which is the Church.
Christian marriage and the Christian family build up the Church: for in the family the human person is not only brought into being and progressively introduced by means of education into the human community, but by means of the rebirth of baptism and education in the faith the child is also introduced into God’s family, which is the Church.
The human family, disunited by sin, is reconstituted in its unity by the redemptive power of the death and Resurrection of Christ.37 Christian marriage, by participating in the salvific efficacy of this event, constitutes the natural setting in which the human person is introduced into the great family of the Church.
The commandment to grow and multiply, given to man and woman in the beginning, in this way reaches its whole truth and full realization.
The Church thus finds in the family, born from the sacrament, the cradle and the setting in which she can enter the human generations, and where these in their turn can enter the Church.
37 Cf. Pastoral Constitution on the Church in the Modern World Gaudium et spes, 78.
— Familiaris Consortio 15