>>513568136 (OP)QRD:
1) Russians - originally slavs + finno-ugoric+balts+nordics mix (mostly Slavs). Only slavs that made an empire compirsing of 110 nations (ethnic Russians still 85% though).
2) Poles - originally slavs + balts + dash of germanics. Had same aspiration to be an empire as Russians, but failed in competition with Russia. That, unfortunately, fosters resentment stemming from lost rivalry.
3) Ukrainians - meme nation, that appeared on a desolated by Mongols lands of Kiev and other modern-day Ukraine Rus' principalities. Mostly consisted from runaway slavs from Russia and Poland that made up mercenary gangs of cossacks that were eventually joined back to Russia. Also has admixture of Turkic blood as other part of modern-day Ukraine (e.g. Azov/ Crimea etc) was long under Ottomans and was liberated by Russians in 1700-1800s.
4) Belarus - slavs + balts mix that had Grand Duchy of Lithuania kingdom that was in union with Poland once, but was Orthodox and used cyrilic alphabet so was leaning towards Russia from perspective of common folk.
5) Bulgaria - admixture of turkish and slavic blood - came from turkish origin, but mixed with slavs on the way. Orthodox and cyrilic. Were re-created from ashed by Russian empire as part of Russian victory over Ottomans (as well as Romania and Moldova). Ungrateful though and fought against Russia in both ww's.