The Fathers are those who followed on the footsteps of the Apostles and left us important writings about our faith. I do not know if Orthodox dispute any Fathers as they belong to the era before the split between East and West. Perhaps someone better versed in Eastern theology can elucidate more about that aspect.
Basically, it seems the Catholic Church begins a new era called scholasticism, after which, no new Church Fathers could be named. The Eastern Church maintains that the era of Church Fathers never ended, and thus, any newer writer could be considered if what they write agrees with earlier writers.
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