I've done some more checking. As I said before, John the carpenter did not marrry until 1893. Both 1901 and 1911 censuses have his son as Willie born 1895/6.
Willie Loveday is registered in Henley RD 3rd quarter of 1895.
He died in 1980 registered Croydon. Amy died in 1976 in Oxford.
It is theoretically possible that John had another son, William, earlier in 1889, but the birth is not registered.
The questions are - do you have a death date and place for your grandfather? What is your evidence for his birth in 1889?
If you are absolutely certain about the William /Amy marriage, the first step woyld be to get their marriage certifciate and check their ages and fathers and mothers.