In the 12th century there was a papally approved Catholic community known as the Order of Sion with houses on Mt Zion, Mt Carmel and Calabria. Some modern writers have tried to connect this Order of Sion with the Priory of Sion mentioned in the book "Holy Blood and Holy Grail". However this is highly speculative and doesn't seem to hold water when examined more closely. The mother house of this Order of Sion was the Church of St Mary of Sion which included the Cenacle during the time of the Crusader Kingdom of Jerusalem.
This Cenacle was to become the mother house or Messianic Synagogue of the early Jewish Church of the circumcision. This was the place called Zion from which the mystery of the Eucharist would radiate out to the four corners of the earth. At the time of Constantine the Jewish Church broke with the Pope and Rome after the visit of eight Jewish Christian Bishops (all belonging to the descendants of the Holy Family) to Pope Sylvester I around 321. For a number of years the mother Church on Mt Zion was not in unity with the Gentile Church in Jerusalem and St Cyril of Jerusalem was unable to preach from there in 348 (see Bargil Pixner "Church of the Apostles Found on Mt Zion"). However in 394 under the guidance of St Porphyrius, a Jewish Christian from Thessalonica, the Jewish Community on Zion was reconciled with the Gentile Bishop of Jerusalem John II. Pixner states:
The reconciliation was finalized when the bishop of Jerusalem, John II (served 387-419 A.D.), blessed the altar of the Judeo-Christians (propitiatory, Hebrew kapporet), now in the Theodosian church, on the feast of Yom Kippur (September 15), possibly 394 A.D. On that occasion Bishop John gave a most astonishing sermon full of Judeo-Christian symbolism. In it he praised again and again the great merits of Porphyrius the Israelite.It would seem this was when the Jewish Christian community and congregation who would seem to be run along the lines similar to those found in the Celtic Church as a monastic community with a lay or clerical Abbot (Abba/ Abouna) of Davidic ancestry as the head with monks, clergy and laypeople as members. This when integrated with the wider Church was known as the community or Order of Zion (Sion). The early monks of Mt Carmel also belonged to the Order of Sion and it was to Mt Carmel that the Jewish Christian 'Order of Sion' retreated when the Persians invaded Jerusalem in 614. It is the hermit monks of the Order of Sion community on Mt Carmel that are the spiritual ancestors of the Carmelite order which was formally established in the 13th century. Some of the Order of Sion retreated to the lands in the Indian Ocean and were known as the 'Mourners of Zion' when Benjamin of Tudela visited them in the 12th century. Some from this branch of the Order of Sion (who had maintained more Jewish forms and observances) settled among the Jewish communities in Spain and Poland beginning in the 13th century.
When Jerusalem was retaken by the crusaders in 1099 the Order was able to reestablish the house on Mt Zion with the support of Godfrey du Bouillon. In the 8th century the Order of Sion was also able to establish a community in Calabria in Italy where they followed a version of the Byzantine rite. The Order of Sion endeavoured to be among the poor and to remain hidden from sight. The remnant of the 'Order of Zion' is thought to have come under the protection of the Jesuits in Calabria and Sicily. It was this Jewish Christian influence among the Jesuits that allowed the Jesuits to support the Frankists who entered the Church in 1760. Some of the descendants are to found among both the Latin-rite Catholics and Italo-Albanian Byzantine Catholics of southern Italy. It is interesting that two Jesuit priests of Jewish background in the 19th century founded the two congregations with a Jewish apostolate named for Our Lady of Sion. Could the Order of Sion be revived today as the Ordinariate of Our Lady of Sion with its centre on Mt Zion in Jerusalem? Could this future Ordinariate of Our Lady of Sion be open to the descendants of the hidden Jews who feel called back to their Jewish heritage such as the crypto-Jews of Calabria and Italy, as well as those in Spain and Mexico and the Spanish speaking world, as well as those in Portugal and Brazil and those in many countries who are feeling this mystical call to their Jewish ancestral roots and practices?