James W. Preston, born in either 1819 or 1820, was enumerated in Harford County, Maryland in 1850 and 1880 together with his wife Hannah and their children. In the 1850 census James was enumerated in August with his wife and children and in October with his parents and siblings. That wasn't an uncommon occurrence in the early years of the US Census, when parents often listed all their children even though some had already married and left the family home.
That October1850 Preston family group consisted of: Moses, 50; Blanche, 50; James, 30; Elijah, 28; George, 23; John, 21; William, 20; Sarah, 18; Rachel, 14; Charlotte, 12 and Robert, 10.
A different James Preston, born in 1810, was also enumerated in the US Census of 1850 but he was single and living in Anne Arundel County.