Here is Robert's family in the 1911 census index (details are pay-to view):
Stockton, Durham
Robert WELLS (born Scruton) - 40
Frances WELLS - 40
John Thirkell WELLS - 18
James WELLS - 13
Albert WELLS - 11
Frances May WELLS - 9
Christopher Edward WELLS - 8
William Henry WELLS - 6
Thomas Mathew WELLS - 1
Thomas M WELLS m. Jessamine M NELSON, Mar qtr 1933. (Darlington 10a 31)
In the full GRO index, I have found births in the Durham area for 2 of the children you mention, which give their mother's maiden name as NELSON.
Hope this helps!
Rambler