
You really need a subject for this sentence, so "I never knew...". Also, stylistically, I would say that "I never before knew" sounds slightly more natural, although don't ask me why!
Even less relevantly, I wish school hadn't crushed my interest in German, especially as I'm friends with so many Germans now!

This is a Mark Twain quote, he's quoted exactly this way. I wouldn't dare to change it :)