Desmond said Kelvin was dead.
You are suggesting that Ethan is part of the boat group and that Goodwin knows nothing of Ethan or the boat people? It may be circumstancial, but Nathan saying he was from Canada and "Ethan" saying his name was Ethan and that he was from Canada is suspect. In both cases, an outsider infiltrated a group of the survivors and worked to abduct some of them. I think Goodwin and Ethan were part of the same group.
Also, from the evidence we have to work with, it would seem that Ethan and Goodwin did not know about either of the bunkers we know about. Desmond's words and actions indicate that he has not seen anyone except Kelvin since he shipwrecked [although he could be lying, I suppose]. Goodwin looked suprised when the tail-enders found the door to the second bunker.
Okay okay. Has everyone come into an agreement about the following thoughts:
Ethan and Goodwin knew each other and were apart of the Others
Ethan and Goodwin knew each other and were apart of the Boat Group
Ethan and Goodwin knew each other and were apart of the Other and Boat Group as they are the same
Ethan and Goodwin did not know each other and each was apart of either group
See the Boat Group had normal clothes which would make more sense for Ethan and Goodwin to have normal clothes rather then being a part of the Others because they had rags moreless.