Taking Ernest's assertion that his mother and 5 of his brothers were dead by 1916 at face value then, as we know that Walter was still alive (d1917) and probably Charles (d1917) and assuming he wasn't including William (died young ?) as one of the 5 it would seem to imply he was referring to Frederick, Harry/James, Thomas, Edwin/Edward and Arthur - are dead.
Frederick is dead. Nothing certain for the others and the big problem is that Harry's wife is still listing herself as married after 1916 even though Harry doesn't seem to be with her.