lithuanians are so pretentious to call their language baltic

I seriously don’t get why they call their language a baltic language and then say it’s related to ancient prussian but also it’s one of the baltic states which are supposed to be slavic countries along with Poland, Czech, Slovakia and others but they say they just share the same sea. Like wtf? Even as a redneck I know the baltic states also include a lot of countries that are not even baltic. They also claim a whole dialect is their language just for the numbers to make their nation look bigger.