It's not entirely clear, but for simplicity I usually say that I became head admin at the beginning of 2011, a little over a year after the forum was created.
The forum was originally located at bitcoin.org/smf, then forum.bitcoin.org (hence the redirect), and finally bitcointalk.org. Fun fact: The name "bitcointalk" was invented by Jeff Garzik, and he's the one who bought the domain.
So based on the quotes above (first by Sirius), It's safe to say that there is pretty much no relation between them and they never met face to face.
Or maybe they don't give much publicity to their relation. People who are near, are (or were) in touch or know Satoshi could be in danger, so for them, it's better to be discreet about it. It's only speculation from my side, but I can fantasize more than just what these quotes say.