User blog comment:Heathharris09/Ed and Al's Souls???/@comment-1318060-20100620170842

Unfortunately, all we know for sure is what Arakawa has told us. We can speculate about it, but it'll mostly be conjecture. Educated conjecture, but conjecture nonetheless. They do appear to have a connection, since Al's Gate is connected to Ed's Gate. I don't believe they would have offered the explanation they did if that weren't the truth. Arakawa was trying to tell us that their souls got crossed during the tragedy as an explanation as to why Al's body was still alive and why Ed could see it when he entered the Gate. Personally, I believe it's at least partially because Edward used his own blood to bind Al's soul, while other soul bindings presumably used the blood of the person in question. Related by blood, bound by blood, the brothers crossed their souls.