Hewlett is the son of James Long (1786-1849) and Sarah Sallie Rusco (1787-1847). He married first, Martha A. Walters (1835-1862)in June 1856 in Brooklyn, Kings, New York. Several years after her death he married Ann Amelia Brush July 31, 1867 in Huntington. They had two sons, Hiram Hewlett Long, and Frederick James Long.
Hewlett mustered into the Union Army, Civil War, Aug 27, 1862. First Lieutenant, Co E NY 127th Inf. Reg. Sept 10, 1862. Promoted to full Capt. Feb 22, 1864. Mustered out June 30, 1865, Charleston, So. Carolina. His wife Ann Amelia received Civil War pension.