As soon as they first said his father had been divorced I wondered if there was another family.
One thing that was so different was that for a lot of us I think (I know many here are of an older generation though) we look back on resources like the 1911 census with interest and somewhat more detachment from closer family, looking for grandparents, great grandparents, even great great grandparents... but to look on there and see your own father, your sister you never knew and to see another sibling who died and to get emotional over that was sad to see.
I also wonder if they were able to find any information about his brother's father, like bastardy records or something. Somebody might have looked into it.