Any idea where your g-grandfather was born?Here are the "John Fureys" ages from 7 to 12 that are in the index of the 1901 UK census.
First Second Age Where Born Admin County Civil Parish John Furey 7 Mddx Hampstead London Hampstead John Furey 9 City & County Of Liverpool Essex John Furey 10 Yks Sheffied Sheffield Sheffield John Fury 7 Manchester Lancs Manchester North Manchester John Fury 8 Lancashire Liverpool Liverpool Liverpool John Fury 9 Warrington Lancashire Warrington John Fury 10 Brecs Brynmawr Brecknock Brynmawr John Fury 11 Durham Hebburn Durham Hebburn John Fury 12 Essex S Ockendon Essex South Ockendon John Fury 12 Worcester Belbroughton Worcestershire Worcester
If he is one of the above (and he should be, if he hadn't emigrated!) you can then find out who else is in the family. I've included the wide age range due to the possibility of the wrong age being filled out on the form.The 9 or 10 year olds are your best bets.You should also perhaps give BMD details on his 8 children so that others can check for connections.Good luck.