I recently discovered that they were all in the same section of Vienna in 1913 at the same time. I was hoping to further research what they were doing/ thinking at this time.
The early bits of The Rise and Fall of the Third Reich discuss Hitler's time in Vienna- what he was learning/thinking. There is also a brief part that takes note of Stalin and others in Vienna at the same time.
There's this book about 1913, which talks about some of the people you're asking about in a few episodes. I really recommend it, it's an interesting cultural history of this one year.