I’m researching Kogan=>Cohen from Zvenigorodka, Cherkassy Region, Ukraine. Of 1,711 people in the Yad Vashem data for this town, 28 are Kogans and 13 are Kagans.
I assume both are Cohanim, but how closely are they related? Are these just arbitrary transliterations into Russian/Ukrainian and potentially close relations, or is there a definite split many generations ago?