I never before thought about the similarity of the two words. 'Freunde' is 'friends' and 'Freude' is well translated with 'joy'. The word 'Bruder' now nearly exclusively means brother as a close relation. One century ago or more it still could by used in a broader sense meaning a very close friend. That's how Schiller used the word, but this use is completely out of fashion today, it only survives in that sense in composite words.

Wolfgang