The way I know it, the story went like this:
In the 1990's, Starmen.net was formed. It grew into the big site we know today.
Mato co-founded the site, and in 2008, he made a blog to showcase random Earthbound facts that weren't SM.net front-page worthy, per se, but that were still cool and worth recording somewhere. That blog is Earthboundcentral, and this forum was built onto it a year or two back.
It's not that they separated; they weren't ever really together in the first place, as far as I can recall.
(If somebody remembers differently, please correct me.