One more thing: when James Roy Grant died (16 July 1873), the person who made the report was A.J. Grant, Esq. That seems to confirm that the land (SSR II, lot 15) on which John J. Grant lived in 1874 was his father's lot. If you look at it on the 1874 plat map, lot 15 is divided between John J. Grant and A.J. Grant, Esq.
Also, the 1851 census for the 2nd Cons. includes James and wife Catherine and calls the Grants there "1st settlers."