- Most Rev. Robert J. Coyle, Vicar for the Eastern Vicariate
- Most Rev. Richard G. Henning, Vicar for the Central Vicariate
- Most Rev. Luis Miguel Romero Fernandez, M.Id
- Most Rev. Andrzej Zglejszewski, Vicar for the Western Vicariate
- Most Rev. John C. Dunne, D.D. (Retired)
- Most Rev. Emil A. Wcela (Retired)
The Office of Auxiliary, or Assistant, Bishop came into the Church around the sixth century. Before that time, only one bishop served within an ecclesial province as sole spiritual leader of that region. Those clerics who hold this dignity are properly entitled Titular Bishops whom the Holy See has simultaneously assigned to assist a local Ordinary in the exercise of his episcopal responsibilities. The term Auxiliary refers to the supporting role that the titular bishop provides a residential bishop but in every way, auxiliaries embody the fullness of the episcopal dignity.
Although the Church considers both Linus and Cletus to be the first auxiliary bishops, as assistants to St. Peter in the See of Rome, the first mention of the actual term auxiliary bishop was made in a decree by Pope Leo X (1513-1521) entitled de Cardinalibus Lateranses (sess. IX). In this decree, Leo confirms the need for clerics who enjoy the fullness of Holy Orders as assistants to the Cardinals-Bishops of the Suburbicarian Sees of Ostia, Velletri-Segni, Sabina-Poggia-Mirteto, Albano, Palestrina, Porto-Santo Rufina, and Frascati, all of which surround the Roman Diocese. Because the Cardinal-Bishops resided mostly in Rome, serving the popes as senior advisors, these vicars governed the suburbicarian sees in their absence.
But in the broader sense, the origin of the office of Auxiliary Bishop came into the Church when Islam overtook North Africa and the Near East in the first millennium, resulting in the collapse of the local Catholic churches across the southern Mediterranean basin. Those Christians who were not martyred for their faith converted to Islam or fled to a sure shelter in Europe. A great many of the bishops of this region made their way to safety in Rome. In due time, however, most of these deposed bishops permanently resided in the Eternal City, living at the Papal Court, or at the seat of the Roman Empire. They remained there, living in great style and comfort, until death, but their formal diocesan titles did not die with each, as one would expect.
Not willing to relinquish both her rights to, and presence in, these overtaken dioceses, the Holy See continued for centuries to nominate men to the vacated sees in hope that one day the Church would return and she could then illustrate a continuity of Apostolic Succession throughout the duration of the Islamic occupation. During this prolonged period, these many dozens of dioceses in exile were officially seated in Rome where the clerics assigned to them had little to do. In time this caused problems for the Church, which continued to resist the presence of so many bishops at the Papal Court. And by the twelfth century, even sitting bishops of major European sees also preferred life at the magnificent Papal Court to the simplicity, and sometimes harshness, of their own dioceses; so much so that a succession of popes of this age had to finally order bishops to return home under pain of excommunication. The presence of exiled titulars only compounded the situation.
Not knowing what to do with so many idle bishops, the popes of the twelfth through fourteenth centuries began to make use of the keen abilities of these clerics by assigning them to temporary governance of vacant sees in Western Europe. The local prince who coveted the wealth and influence enjoyed by the local Diocese or Abbey-Nullius often blocked formal replacement of a permanent residential bishop in many of these wealthy and prestigious dioceses upwards to a decade. And so, in this impermanent role the titular bishops more or less served as temporary papal vicars but each retained their jurisdiction over their own titular see from long abandoned North Africa and beyond. This policy continued for several hundred years and out of it grew the modern canonical understanding of the role of both auxiliary bishop and vicars apostolic.
It was not until after the Council of Trent (1543-63), that Pope Saint Pius V (1566-72) decreed that thereafter, auxiliary bishops could only be assigned to Cardinals who governed major sees or to archbishops with vast territories under their spiritual care. At this time, the term auxiliary was generally replaced by that of suffragan but when larger ecclesiastical provinces were later sub-divided into numerous smaller dioceses, this latter term was then affixed to those newly created residential bishoprics that in turn reported to the senior archbishopric of the region (the incumbent of that see thereafter referred to as the Metropolitan-Archbishop of that province) and as such, the term auxiliary returned for those prelates working as assisting bishops to a cardinal or archbishop. Pope Pius’s decree also limited the appointment of auxiliaries to those sees that were financially able to properly sustain a second, titular, bishop in that place. The rights, privileges and responsibilities of these clerics were thereafter carefully defined in the writ of appointment of each individual prelate, each differing dependent upon the specific needs of each local Church.
It was after Trent, therefore, that the law finally required a cleric, who was not already a bishop at the time that he was named an auxiliary of a specific place, to be vested with one of the many vacant sees from North Africa or the Near East. From the earliest days of the Church, it had always been understood that no one could enjoy the fullness of Holy Orders without being assigned a specific diocese over which he either actively or passively governed. In fact, when a priest is ordained to the episcopacy as an auxiliary bishop, as in the case of Bishop Hundt, one of these ancient long-lost sees of the Mediterranean basin is always assigned to him. Today these dioceses are known collectively as the sedi titulari (or titular sees). The titular see of Tarasa in Byzacena (Tarasensis in Byzacena to give it its proper Latin title) has been conferred upon Bishop Hundt as his own canonical diocese. Thus continues the Apostolic Succession of the See of Tarasa even though more than a thousand years has passed since a Catholic bishop has actually sat in governance there.
The current Code of Canon Law defines an auxiliary bishop as one who does not possess the right of succession of that place (4031). It likewise stipulates that all auxiliaries of a diocese be simultaneously appointed as either Vicars General or as Episcopal Vicars (4062) and specifies within the rescript of appointment what privileges and obligations of the office that new auxiliary will enjoy (4051).