However, we are “sister Churches.” This is the term used in John XXIII’s letter to Patriarch Athenagoras of Constantinople. The term was also used by St Pope Paul VI and Patriarch Athenagoras in 1965, when both represented their sees. Vatican II also uses the term “sister Churches” to describe the relationship between particular Churches. Here is an excerpt from the Note on the Expression “Sister Churches” put out by the Congregation of the Doctrine of the Faith:
“in the East there flourish many particular local Churches; among them the patriarchal Churches hold first place, and of these, many glory in taking their origins from the apostles themselves. Therefore, there prevailed and still prevails among Eastern Christians an eager desire to perpetuate in a communion of faith and charity those family ties which ought to exist between local Churches, as between sisters.”
The See of Rome, a particular Church. The See of Constantinople, a particular Church. According to Popes of the last 50 years, Vatican II and the Congregation of the Doctrine of the Faith, Rome and Constantinople are “sister Churches” not “father and daughter Churches.”
ZP