Jam,
Did you know that the Holy See of Constantinople ,the Holy See of Antioch,the Holy See of Jerusalem,the Holy See of Alexandria,and of Russia ,Greece,Serbia,Cyprus,Romania,Bulgaria and Georgia which all happen to be in union with each other which in turn makes them all One ,did you know that it is a fact that each of these churches has its own head bishop who is not under any other higher bishop or church authority ,which means for instance that the ancient and Holy see of Constantinople is self governing and its head bishop which is also called the Patriarch is basically in charge of his own See and has no right to interfere lets say for instance in the affairs of the Holy See of Russia or Cyprus etc.
The Patriarch of Constantinople as i mentioned earlier is not under the authority of another bishop because the See is mature and is able to function on its own with its considerable amount of Bishops ,priests ,deacons and laypeople to self govern it,
While at the same time being in full communion with the other Sees of these many different Countries making them One church with the same faith.