The Church teaches this about marriage and the family:
Christ chose to be born and grow up in the bosom of the holy family of Joseph and Mary. The Church is nothing other than "the family of God." From the beginning, the core of the Church was often constituted by those who had become believers "together with all [their] household." When they were converted, they desired that "their whole household" should also be saved. These families who became believers were islands of Christian life in an unbelieving world. (1655)*
In our own time, in a world often alien and even hostile to faith, believing families are of primary importance as centers of living, radiant faith. For this reason the Second Vatican Council, using an ancient expression, calls the family the Ecclesia domestica (domestic Church). (1656)
The first centuries of the Church were marked by families who lived the Faith. They were true disciples of Christ. Although they encountered problems living in pagan societies, they were notable examples to others who encountered them. These Christian families were true lights to the world; they were a leaven in their communities. By their faith and perseverance, they changed the world. Many of the values, with which we grew up, can be traced to Christ's moral teaching that the first Christian families lived each day.
The domestic Church begins with married couples. Their marital love has God's love as its source and therefore grows outward. When they are given the gift of children, they become a family capable of the same life as the first Christian families.
It is here that the father of the family, the mother, children, and all members of the family exercise the priesthood of the baptized in a privileged way "by the reception of the sacraments, prayer and thanksgiving, the witness of a holy life, and self-denial and active charity."
Thus the home is the first school of Christian life and "a school for human enrichment." Here one learns endurance and the joy of work, fraternal love, generous—even repeated—forgiveness, and above all divine worship in prayer and the offering of one's life. (1657)
True Christian families today are a light to the world which needs them very much.
*Note: Numbers in brackets refer to the numbers assigned to paragraphs of The Catechism of the Catholic Church.