I don't know the Sepchenko family of Kief, though my grandfather did grow up there. My great-great-grandmother was Thelma [not exactly a Ukrainian name!] Sepchenko (Sepchanko, Sipchenko) Michalenko, married to George Michalenko. I am not sure that they ever came to the United States. Three of their sons did and lived in Kief or the near vicinity.
A Sam Sepchenko married Marina Michalenko, daughter of Peter Michalenko, 7 November 1905. They had five children. The California online death index gave the maiden name of Sam's mother as Krowchenko. No first name for either his mother or father is given.
Hope this is some help. Karen T