Unless I am seeing things, I believe that the image in the background as each man speaks in the commercial is one of the same man in the often shown picture with Kerry in the group. It seems evident that the man in the picture and the one speaking in each instance are the same person; only older.
I think that makes it clear that these people were with Kerry in some capacity.
My guess is that most of it could be proven quite easily.
My neighbor served on PBR boats (?) in the Mekong delta. He tells me that it was rare for him to go out with the same crew on every patrol.