A woman contacted me recently who is evidently a fourth cousin; we have a set of great-great-great grandparents in common. She sent me a scan of an old undated photo and told me that the second man from the left was her great-great grandfather, Frederick Duntemann 1846-1927. She thought that one or more of the other men were Frederick's brothers. What did I know?
Not much. But it's an interesting sort of detective work, this family resemblances stuff. I do know that my great-great grandfather Heinrich Duntemann 1843-1892 had four brothers, all of whom long survived him, who died of an infection from a farm injury at 48. I have photos of two of his brothers, William Duntemann 1849-1921 (left) and Hermann Duntemann 1859-1933. (right). William's photo was taken when he was in his sixties, as best I know. Hermann's was taken when he was 26. If I had to guess, I'd say that the leftmost man in the group photo was William, and the rightmost was Hermann. The remaining man may have been Louis Duntemann 1851-1928. I can't tell, as I've never seen a photo and know very little about him.
Well, they certainly look like brothers to me, and in fact far left and third from left could almost be twins. The guy on the right seems like a shoo-in for an older version of Hermann. That said, I'm not sure how fair it is to say: "This is a photo of the four surviving Duntemann brothers, circa 1920." Hermann left no descendants, but at least a hundred people descend from the other three brothers. If I say that that's what it is, all those people will likely take my word for it. (I'm the de facto family history expert, simply because I know a little and everybody else knows nothing.) It would be great to have such a photo of the four brothers, and maybe I do. But I think I have to be real damned careful about saying so. Uncritical acceptance of expert opinions is dangerous, when the experts know only a little more than everybody else but still want the prestige of expertise.
So I will lead by example: These guys may just possibly have a greater-than-zero chance of perhaps being your great-great (and perhaps greater) grandfathers. It is impossible to know. We might wish it were otherwise, but wishin' don't make it so.