can you tell me any other language belonging to the same family?
Polish, Kashubian, Upper and Lower Sorbian and Slovak.
Czech language
This branch includes Polish, Kashubian, Upper and Lower Sorbian and Slovak. 
what is the language in the czech republic Czech. how is it classified? It is a member of the West Slavic sub-branch of the Slavic branch of the Indo-European language family. This branch includes Polish, Kashubian, Upper and Lower Sorbian and Slovak. where else is this language spoken? The United States of America.
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Czech language [SEP] Classification
Czech is a member of the West Slavic sub-branch of the Slavic branch of the Indo-European language family. This branch includes Polish, Kashubian, Upper and Lower Sorbian and Slovak. Slovak is the most closely related language to Czech, followed by Polish and Silesian. The West Slavic languages are spoken in Central Europe. Czech is distinguished from other West Slavic languages by a more-restricted distinction between "hard" and "soft" consonants (see Phonology below).