Traditionally children always get the father's first name for their middle name, plus "vich" as a ending. I have never heard the name Eovich, that is why I asked you. Good, news is that if he had changed his name to John, his original name most likely was Ivan, thus you fathers middle name would be Ivanovich. Middle name may have been shortened to Eovich later. Of course, I could be wrong if your grand father's name was of a judaic/hassidic origin, for I am not familiar with those names.