There has been some speculation on whether Joe and Kelvin are twins or one of them is using a fake name.Damon and Carlton say in their podcast that Joe Inman and Kelvin are the same person. They say the Joe's name is never mentioned in Sayid's flashback and they made up "Joe" because it would be used in TV Guide or other schedules and if they called him Kelvin, everyone would have realized he was Desmond's hatch partner way back then.
Well...that changes things slightly. Forget the whole 'bad twin' theories out there. This leads me to think there will be a military connection with Dharma. We have Kelvin, Sayid and now Desmond who all have military backgrounds...each from a different army. Hmmm.