Going through the censuses and GRO index, George's mother was Mary Charlton.
John , son of William Wilkinson, and Mary, daughter of George Charlton, married on 10th June 1860 in Stockton.
John was baptised on 3rd June 1838, in Billinghay, Lincolnshire, son of William and Elizabeth.
Trees vary on his mother, but one has Clarke and there is a John, mmn Clarke, in Sleaford District in 1838.
Sleaford is 10 miles from Billinghay and so could be correct.
There is a marriage of William to Elizabeth Clarke in Billinghay on 20th November, 1813, although quite early for John's birth date.
David