I can't find any Dots/Dorothys of a suitable age on the censuses/BMD index etc at the moment, but yes, she could well be a grandchild, given that his second wife is the same age as some of his older children!

Very interesting. Two of his sons by Mary Ann were deaf and dumb from birth - Henry and Thomas. They were actually late discoveries for me, as they don't appear with the family on any of the ensuses, but living instead with various relatives or as lodgers. At first I thought perhaps they had been sort of 'given up' by their families, but increasingly I think this isn't the case. And having someone from such an organisation certainly makes me think not.