1850 Grayson Co., KY
Basil Alvey, b. KY, 66, farmer
Julina, b. KY, 24
Martha, b. KY, 20
William Newton, b. KY, 16, laborer
He won't appear on a 1840 Census since he was too young to be a head of household.
In cases like this, it's best to look for his death certificate and obituary.
William Thomas Newton
Born: May 4, 1835, Hardin Co., KY
Died: July 5, 1911 [probably Williamson Co., IL]
Buried: Rose Hill Cemetery, Marion, Williamson, IL