Jacob was born in near Belfast in Waldo County, Maine (which at that time was still part of the Commonwealth of Massachusetts) to Job and Susanna Durgin Allard. On December 19, 1819 he married Sarah "Sally" Thurston in Eaton, New Hampshire. In New Hampshire were born their 10 children: Alvah C, Job, David, Eleanor Jane, Jacob, Martha Ann, Joseph, Elizabeth Ann, Rosanna, and Alvah Cross (named after the first son who had died). In the 1850's part of the family came to Warren County, Ellison Township, Illinois; Sally died there in 1856.

Joseph, David, and Eliza (Elizabeth Ann) were the only children who settled in Illinois.

First son Alvah (1820-1840) is buried at Eaton, Hew Hampshire. Second child, Job, married Mittie Ann Thurston and they are buried at Eaton New Hampshire; they had two children William Otis (buried at Eaton) and Daniel Austin (1848-1929, buried at Colo, Iowa). Third child David married Harriet Patch in New Hampshire and they, along with their first three children (Frank, Rose Ellen and Josephine) also came to Warren County Illinois where four more children were born (Orin D, Charles H, William, Arthur E). Fifth child Jacob married Sarah and two children (Alphine and Sam) were born in Massachusetts. Joseph married Fannie Wornom and they spent their lives in Warren County and are buried at Center Grove Cemetery in Kirkwood; their children were Clayton, Blanche, Cora, Myrtle, Chester, Mittie and Pearl. Eliza Ann married Bradley Davis and had two children (Gilbert and Esther); Jacob was living with her when the 1870 census was taken. Next-to-last child Rosanna married Frederick Balding and moved to Oregon where they had two daughters (Grace, 1882; Jennie, 1884). Last child Alvah Cross married Florence Smith and moved to Iowa; he is buried in the Colo Cemetery in Story County, Iowa.