Hello again
I too have the same information, I do not think there are any more children.
The daughter as you say was taken into care, perhaps Mary could not cope, hence the two sons with the grandparents, and perhaps Mary working as part of a larger staff, perhaps a cook, at a house in Anglesey, North Wales.
It gets more intriguing doesn't it?
Thank you again Carole
Jan
(PS I went on the to Great War Forum, and the above info was given to me by someone on this forum)