Only eastern Latvia (Latgale) were part of Polish-Lithuanian commonwealth for a short period of time.

Lithuania today is not the same as Lithuania back in the days.

Today, Lithuanians and Belarusians care about Lithuanian heritage more than Poles, Latvians engaged in endless fights  proving each other who were more Lithuanians in historic context.

The Grand Duchy of Lithuania (mostly present day eastern & central Lithuania (Aukstaitia) and Belarus) existed between 1250-1795. Eastern Latvia, north Ukraine were also part of the Grand Duchy for a short period of time.

Polish-Lithuanian Commonwealth existed between 1569-1795 – for 226 years only. Neither Lithuanians nor Belarusians are fond of that union. The union was necessary to resist Muscovite western expansion.