Another possible union is the unification of Belarus with Russia. While Belarus currently remains an isolated country in Eastern Europe, it shares a border with Russia, and its diplomatic stance is closely connected with Russia’s. Belarus also seems to follow Russia’s foreign policy very closely, establishing strong economic, military, and political connections with the Russian Federation. The Russian federation already has some semi-autonomous republics within it, so Belarus could be the next one to join.
“Belarus Russia Locator” By Russavia (CC BY-SA 2.5) via Commons Wikimedia