Hi Annette
I was really interested when you mentioned that our grandparents mother died when your Gran was young, because the photo I have, which I was always led to believe was their mum, is of an elderly lady. Perhaps she wasn't their Mum at all, but could she be Charlotte Durran instead? She's certainly wearing a late Victorian dress.
Do you know anything about their brother, Frederick? Did he die young?
My Grandad did mention people working at Blenheim Palace, but I don't know who, when or in what capacity.
Regards
Margaret