Hi Patrizia

thank you for the census information.
We are still hoping you will answer some of the other questions we asked earlier.
So to recap these:
From the marriage certificate of 1869, what was the name of Margaret Potts' father?
Have you traced Margaret Potts' family in the 1861 and 1871 censuses to see if George is possibly living with them under the surname Potts?
Under what surname were the two daughters of William Robson and Margaret Potts registered?
Have you looked for George's birth under the surname Potts? You say you cannot find his birth, but how many of the births under the name George Robson or George Potts in Sunderland have you actually checked to find out the names of the parents?
You say you are concentrating on births 1856-9, but the variety of ages given on the censuses suggest that you might have to spread the net a little wider.