Three questions, hope you dont mind Bertram born in 1898 and his brother Sidney

[Ruskie]

Might the sitting boy have his legs and feet close together but with one slightly in front of the other?

If you look at the width of the other boys legs, the sitting boy's "leg" is a lot wider, which makes me wonder if there are two legs side by side?

I can't see enough detail to see two distinct shoes with one perhaps in front of the other, but I suppose if the legs and feet were really close together, then it could look like there was only one foot?

[Gadget]

I'm in the middle of doing another restore at the moment but this is what I've got from your image without a repair.

Is the surface rough or shiny?

Gadget

added - looking at it straight on, the one knee is further back than the other knee - I'm now wondering if there was a partial amputation - tricky 

[Geoff-E]

It depends on the circumstances of the (possible) loss of limb.

I found an 1889 newspaper report concerning an aunt of my mother's, and how she lost a leg while walking on the railway. The friend she was with lost her life.

Perhaps such a report exists for the lad in the photo.

[warpo]

I've been sent another image. I told the owner of the image to take it to a professional photographer, but they went ahead and took it out of the frame and took another picture for me. Can't believe they did that, but this is their result. It is a little clearer.

[Sinann]

Looking at that copy, I think he could be sitting with his lower body twisted away from the camera and upper body towards it, (showing his good side) but if there is a second leg behind the first I can't see where it could fit.
It's difficult to see if it's the inside or outside of the shoe we are looking at.
His near hand seems to be resting on a cushion or arm of the chair.

[Spidermonkey]

Do you have Bertram on the 1939 register - there is always a chance that his profession or associated comments might give an indication that he was disabled in some way.

[warpo]

On the 39 register Bertram was running a Sweets, tobacco and provisions Shop.

Sidney on the other hand was a Steel Worker, Heavy Worker.

[Ruskie]

It looks like one of those overpainted photos. Depending on the skill of the 'artist', detail can be lost and I think this may be the case here?

I still think that one leg is behind the other - you can almost see the shadowing of the shoe behind.

The appearance of one knee rather than two adds to the illusion. I think that the 'artist' just did not define the legs/knees/shoes very well.

[Gadget]

There was a thread a while ago abut a lady with a possible missing foot.

Some of us were convinced that it was missing - she was diabetic, I think.  It turned out that it was the way she had placed her foot. A photo turned up of her when she was older  with both feet.

Is there any chance of finding another photo of him?