The idea is that George Llewellyn Lewis birth reg Mar qtr 1888 West Ham may be the same person as the George H Lewis you found aged 3 in 1891.
There is no birth for a suitable George H Lewis, and George Llewellyn Lewis is a good fit in terms of age and birthplace (Custom House, same as for his presumed sister Lily Elizabeth who later married John Norfolk, according to her 1901 census entry with the Gibbs grandparents when she was 10 b Custom House).
Moreover, George Llewellyn Lewis and his wife Louisa Ann nee Ashby named a son George Edwin (1913) and a daughter Lily Elizabeth (1910) - familiar given names in your Lewis family.
Obviously it would mean that the middle initial was wrong in the 1891 census, but we already know that the middle initial for his father Edwin was also wrong (J rather than G for George).