Is the word although a realtive pronoun?

No, the Word 'although' is not a pronoun. The Word 'although' is a conjunction, a Word that joins Words or groups of Words together.

Example: I liked Starlett's new movie, although I like her first film better.

A pronoun is a Word that takes the the place of a noun in a sentence.

Example: Starlett has a new movie in which sheplays a movie star. (the pronoun 'she' takes the place of the noun 'Starlett' in the second part of the sentence)