I am also researching James, son of Giles Stevens. My information, taken directly from the Stevens family Bible is:
Yily (Giles?) Stevens, born unknown;
James, son of Yily, b 1 March 1725;
Henry, son of James, b 14 July, 1771 (married Eleanor);
John J., son of Henry, b 29 Jun 1794 in VA (married Elizabeth Collins 25 Aug 1817 in Ross Co. OH);
John James, son of John J., b 7 July, 1821 in Clinton Co OH, (married Jane Moon 11 Dec 1842 in Clinton Co, OH)
George Thompson, son of John James, b 18 Mar 1849 in Howard Co. IN, (married Parthena Modena Weese 26 Sep, 1866 in White Co, IL)
Do you have any of these names?