Why are there so few married saints? And especially, why are there so few who were canonized precisely as married persons? Most married persons who have been canonized have not been canonized precisely as married persons, but as martyrs, or as religious or widows in the case of those who devoted themselves to the religious state or the state of widowhood after their spouse's death (or in some cases, by the mutual agreement of the spouses). And to my knowledge, in the modern formal process of canonization there have been no married couples canonized as such, though two couples have been beatified together, and may in the future be canonized: Luigi Beltrame Quattrocchi and Maria Corsini, and Louis Martin and Marie Celine Guerin (the parents of St. Therese).
The different explanations made for this fact can be grouped into three categories:
(1) There simply aren't many married saints, because of the practical concerns of married life that make it hard to focus entirely on God and his will.
(2) While there are plenty of married persons who are truly saintly, the exemplar of holiness can be seen more evidently in martyrs or religious than in married persons, and therefore it is mostly these who are canonized.
(3) Married saints are not so frequently recognized for what they are.
Sometimes one of this reasons is given as more or less the entire explanation, but I think there is actually some truth in all three of these explanations:
Fewer married saints
(1) St. Paul says, "To the unmarried and the widows I say that it is well for them to remain single as I do. … The unmarried man is anxious about the affairs of the Lord, how to please the Lord; but the married man is anxious about worldly affairs, how to please his wife, and his interests are divided. And the unmarried woman or girl is anxious about the affairs of the Lord, how to be holy in body and spirit; but the married woman is anxious about worldly affairs, how to please her husband. I say this for your own benefit, not to lay any restraint upon you, but to promote good order and to secure your undivided devotion to the Lord. … so he who marries does well; and he who refrains from marriage will do better." (1 Corinthians 7:8,32-35,38) The evangelical counsel of chastity (see Mat 19:10-12) is proposed as a means for securing "undivided devotion" to God. The Christian tradition retains this idea, so that it is said "You would find many among us, both men and women, growing old unmarried, in hope of living in closer communion with God" (Athenagoras, A plea for the Christians, Chap. 33).
Pope John Paul II mentions the fact that most canonized saints are religious as evidence for the value of the religious state as a means to perfection, thus suggesting that the superiority of the religious state as a means for growing in the love of God is a reason for the greater number of religious canonized:
Religious communities are called to the duty of perfection, clearly expressed by Christ in his conversation with the young man: "If you wish to be perfect" (Mt 19:21). Later, down the centuries, the Church's tradition has given a doctrinal and practical expression to these words. The state of perfection is not only theory. It is life. And it is precisely life that confirms the truth of Christ's words: do not the majority of canonized saints come from religious Orders or Congregations?
These words, from a pope who has himself canonized a number of married persons, and who is always careful to note the call of every person to holiness and to the perfection of charity, are not without their weight.
But is the scarcity of canonized married persons due principally to the fact that marriage isn't as suitable a means as religious life for attaining holiness, or is it also due to the fact that marriage wasn't properly appreciated as a means for attaining holiness? Because the married state was not seen as a particularly helpful state for growing in divine love and holiness, those who intended to devote themselves most earnestly to this spiritual growth tended to refrain from marriage if possible, with the consequence that there were relatively few exemplary holy persons in marriage. St. Augustine points out: "[There are some marriages in which the spouses are not divided in heart, but completely devoted to God.] But they are very rare: who denies this? And being rare, nearly all the persons who are such, were not joined together in order to be such, but being already joined together became such (On the Good of Marriage, n. 14). That is, where there are few examples of holy marriages, people will more rarely enter marriage seeking or expecting to become holy through marriage." In this sense, the paucity of married saints is arguably a self-reinforcing prediction. The more emphasis that was put on the religious state as a means to holiness, the more rarely would persons choose marriage in order to become holy. And with fewer persons choosing marriage as a means to holiness, the fewer persons there were who attained exemplary sainthood in marriage, etc. (See my earlier post, Is Marriage for the Weak?).
Visibility of holiness
(2) In the early Church, only the martyrs were regarded the way we now regard canonized saints (the term "saint" itself was then used for all the faithful). In martyrdom the imitation and love of Christ is most perfectly manifest, inasmuch as Christ himself gave his life for the life of the world, and inasmuch as there is no greater love than to lay down one's life for the beloved. As martyrdom became more infrequent, but people still needed contemporary examples of sanctity to honor and to look to, the notion of venerable sainthood was extended to those who did not lay down their lives in martyrdom, but who, as far as possible, left everything to follow Christ, since this is the next most clear manifestation of the Christian call to deny oneself and to follow him.
In fact, the path to holiness always involves the evangelical counsels in some way; if not literally, as in the consecrated state, and least in spirit. All Christians are called to follow the spirit of the counsels. And naturally, the taking up of the counsels both literally and spiritually, as practiced by the saints who embraced the evangelical counsels literally, is the example or model for following the counsels spiritually. And in this sense, religious are already seen as models for the laity, not in the sense that the laity should desire to imitate the exterior form of the life of consecrated religious, but in the sense that they should imitate the inner content, that which is expressed, or meant to be expressed, by the exterior form of life of consecrated religious.
As regards canonized saints' being models of holiness, there could be advantages and disadvantages to having "normal" persons from every state of life canonized. On the one hand, one might argue that people need models of sainthood in the state of life in which they live, and so the model of life provided by the consecrated religious is not adequate for married persons–they also need models of saintly married persons. In fact the idea of saints being models was less emphasized early in the Church than it is now. From the point of view of being models, there is much to be said for having numerous canonized saints from every Christian state of life.
On the other hand, one might argue that canonizing people who seem entirely "normal", could lead to a misunderstanding of the radical call to perfect holiness addressed to every Christian. There is a certain danger of looking at all that the saints have in common with us, becoming self-complacent, and neglecting the need to purify ourselves more and more.
Recognition of holiness-process of canonization
(3) The holiness of "normal," married persons living in the world was less likely to be recognized, because the formal process of canonization required much time and effort, a detailed investigation into the person's life, and accepted miracles. These conditions were more frequently and better provided in the case of religious than in the case of married persons: (a) religious communities have much more people and time for seeking canonizations of their members than normal lay persons do; (b) for much of the Church's history, religious were better educated, and were more likely to be able to write, and thus to become known through their writings, whereas lay persons were only known through more direct contact; thus more recorded information about their life would be available (especially important in cases when the cause for canonization was taken up only many years after the person's death), and there would be more people interested in and supporting the person's canonization.
Supporting this argument, those lay persons who were well-known, and who had more persons interested in their canonization; either on account of their position, as in the case of royalty (St. Edward the Confessor, St. Louis of France, Bl. Karl of Austria), or on account of mystical experiences or visions (e.g., St. Catherine of Genoa, Bl. Anna Maria Taigi), have been, in comparison with their small numbers, relatively frequently canonized.
Biography of married saints
Some books have been devoted to biographies of married saints. John F. Fink has compiled a biography of twenty-four married saints (the link is to the description at the publisher, Alba House. The book may also be purchased at Amazon). These twenty-four saints do include several who were canonized for other reasons, such as St. Thomas More, canonized as a martyr.
A book by Ferdinand Holbock describes briefly the lives of over 200 married saints and blesseds: Married Saints and Blesseds: Through the Centuries.