In the 1920s, in the wake of World War I, Estonia, Latvia and Lithuania became sovereign nations in the aftermath of World War I. They declared independence in 1918, fought independence wars against German Freikorps and Bolshevist Russia, and were recognized as independent countries in 1920.
The newly established countries of Estonia, Latvia, Lithuania and Finland, formerly territories of the Russian empire, were referred to as the Baltic states.
Primarily the contiguous trio of Estonia, Latvia, and Lithuania, Finland also fell within the scope of the term from the 1920s to 1939.

However in The Treaty of Non-Aggression between the Third Reich and the Soviet Union, also known as the Molotov–Ribbentrop Pact, included a secret protocol dividing Romania, Poland, Lithuania, Latvia, Estonia and Finland into Third Reich and Soviet spheres of influence, anticipating potential "territorial and political rearrangements" of these countries.

Estonia's the Barn Swallow, Karolina.
Lithuanian's the White Stork, Paulius.
Latvia's the White Wagtail, Gabriels.
Together, they are the Baltic states.

( The term "Baltic" stems from the name of the Baltic Sea – a hydronym dating back to the 11th century and earlier. )

I wasn't quite sure of the Baltic States's clothing styles during 1920 - 1939. First a idea was made they as males. second was females. But I ended in 2 males & 1 female characters.