Historically, Belarus (back in the days Lithuania) had more conflicts with Russia beginning from early 14th century lasting til 1861 when we had upraising against Russian rule and Russian authorities banned Belarusian language from schools and print.

The very union between Poland and Lithuania resulted from the fact that Moscow was raiding our territories regularly.  Left bank Ukraine (Cossack Hetmanate) joined Russia quite early after upraising of Bohdan Khmelnitsky against Polish rule. Back then territories of Ukraine were given up to Poland by Lithuania during Lublin negotations.

Territories of Belarus were annexed by Russia in late 18th century. The last partition was in 1795

In saying this Belarus and Russia have good relations. Although, we also had nationalistic government in early 90s before Lukashenko rose to power.

In my opinion most problems in Ukraine are due to corruption and socio-economic situation.