Noo one cares about alliances and such stuff. After all, it is a nations cup, not a "we have the same cultures so we can play together"- cup... Russia and Ukraine are actually two (geopolitical) separated countries, so no, don´t let Ukrainian people play for Russia. I don´t see why you are even discussing this, after pages over pages concerning the scotland/gb "issue". If you have relatives and stuff and it is going along with the rules, mix the people.. But in general don´t mix up countries in a nations cup.