Spiritual marriage
Spiritual marriage comes from the idea of "love without sex."
It is been known throughout all cultures as a bond of a man and a woman with its only reason being the spiritual connection between the two and nothing more.
Spiritual marriage in Catholicism
Spiritual marriage is a concept that has a long history in Catholicism.
Catholics have frequently divided themselves into distinct groups, some supposedly more pious than the general population. To give up one's sexuality to enable a deeper devotion to God was a key concept in Church doctrine that demands celibacy of priests, monks, nuns and certain other officials in the Church. The doctrine established a "spiritual marriage" of church officials to their church; in order to better serve God, one had to disavow the demands and temptations of traditional marriage.
The ultimate emulation of this piety by the laypersons of the church was for a married couple to practice a "spiritual marriage" as well. This practice is thought to be most common in medieval times. At times in Catholic history, a spiritual marriage was considered to be a more devout expression of love than a traditional marriage.
Most modern catholics hold the view that, among the laity, spiritual marriage is a part of a traditional marriage, and not a substitute for it.