Celibacy has been encouraged throughout the history of the Church, beginning with several of Paul’s statements. There were locations, by the third century where it was required of bishops, priests, and deacons, at least locally.
In the sixth century, a pair of synods held in Spain ordered clerical celibacy, however, the Church(es) at the eastern end of the Mediterranean did not accept the decress of those synods.
By the ninth century, celibacy was mandatory in most of western Europe (although it was not wholeheartedly practiced).
From the ninth through the eleventh centuries, the breakup of Charlemagne’s empire resulted in a smaller scale replay of the fall of Rome, with most legal institutions (including the Church) suffering a certain amount of fraying at the edges. During this period, despite the calls for celibacy by several Church leaders, it was ignored by many of the clergy.
During the eleventh and twelfth centuries, the Church leadership took a strong stand in favor of celibacy. In the face of so many clergy ignoring the calls for celibacy, it was at this time that the Church passed punitive laws denying the wives and children of priests the right to inherit property (indeed, declaring that the children of priests could be claimed as little more than chattel slaves by the local lords). These acts, in turn, gave rise to the stories that the Church “only” enacted the rules of celibacy in order to acquire the property owned by priests.
Without in any way denying the harshness of the eleventh and twelfth century rules (or trying to deny the corruption that occurred, in many cases, among the local married clergy or the church hierarchy), it is still possible to point out that the concept of celibacy was far older than those events and that the practice of celibacy was not “created” to cement power within the church.
Regarding Anglican/Episcopalian priests and Catholic priests: For several years, now, John Paull II has been accepting Episcopalian priests into the Catholic Church (particularly when they indicate that they have been upset by the willingness of the Episcopalians to ordain women); if these men have already married, the church waives the celibacy rule. Meanwhile, the Episcopalians have been accepting Catholic priests (frequently, those who have left the RCC in order to marry).