Strictly speaking, Ilyich is not part of his given name, it's a patronym, derived from his father's given name (given name Илья <Ilya> produces patronym Ильич <Ilyich>, for male children, for female children it would be Ильинична <Ilyinichna>), so basically Russians have this order: given name, patronym, family name. It's a tradition, so to speak.
So I would leave only Pyotr in given name field and Ilyich can stay as a part of display name. Just a suggestion, nothing more.
I also see cyrillic, original version of his name in the unicode field, does that mean the unicode field can be used, in (extremely) rare cases I suppose, for characters other than kanji? It would make sense after all...
Yet another observation: I understand the field was made primarily for kanji, so in situations like these, having no separation between family and given name looks kind of strange, e.g. when hovering over his name xD
