I can't for the life of me remember where I heard or read this, but back in the mid '90s when Star Wars was getting popular again and the Thrawn trilogy was hugely popular, I saw a speculative story that addressed this. It was speculating about the clone wars and drew from the cloning info we get in the Thrawn trilogy. The author surmised that perhaps Obi-wan was actually a clone of the original Ben Kenobi who had been dead for years. "Obi-wan" was not actually a name, but an alternate spelling for a designation (much like "Artoo Detoo" and "See Threepio") that actually stood for "OB-1" which represented the clone "Old Ben One". Thus, "Ben" actually was his real name and "Obi-wan" was the designation he was known by during the Clone Wars.

The article went on to speculate that the Clone Wars had something to do with a war between the Old Republic and the Mandalorian warriors. The Mandalorians began cloning themselves to increase troop numbers and they began winning. The Jedi ultimately decided that, despite their misgivings regarding the idea, the only way they stood a chance was to begin cloning themselves.

Ah man, I loved when there was so much mystery in the Star Wars universe and you could let your imagination run wild with these crazy ideas about what might've happened outside the films...