Never mind that Roy Webb on the right appears to be about the same height as Charlie Webb standing between the grandparents, forget that the height difference between the two is officially about three inches, take no notice that both of them are standing within close touching distance of said grandparents, heed not that Roy, supposedly the shorter of the two might appear even taller if he stood up straight. Instead, let’s take a look at the old folk.
My guess is that Richard is about three inches taller than his wife Eliza, give or take.
Many argue the reason Charlie appears to be the same height as Roy is that he is further away from the camera and this distance has subsequently reduced his height in comparison to the shorter Roy. Well, there is a rule of thumb guide that can be used to refute such an argument.
How far back from the camera would Richard have stand to appear to be the same height as Eliza?
A metre? Two metres?
Is Charlie standing that far back from Roy?
Of course the assumption here is that the photographer, being an old-fashioned type would have been sure to stand both old folks on a level surface for the pic, not wanting either of them to stumble over uneven ground.

Roy Webb’s enlistment file
You know it makes sense.