Hi,
I am Amy Thursfield. I think the Charles Thursfield who married your great grandmother was my grandfather. He married my grandmother Edith in 1926 and they had 3 children, William, Edna and Charles. William died in 1990.
I don't think any of his children knew that my grandfather had been married before until after he died and they certainly didn't know he had other children.
I am sure my Dad would be interested to know more and if there is anything you want me to try and find out just let me know.
Amy