I could not get very far either.I did find a US Civil War Soldier Record for the Hallowell David H. Ellery. He enlisted 10 Apr 1861 age 30 as a Private, from Maine Mustered out 7 May 1863 Enlisted 13 May 1863 mustered out 21 Jun 1866 born abt 1831 died 23 Apr 1899
The entire family seems to have disappeared, at least from Maine.I have a few more Maine sites to explore.
Have you tried local historical societies?
Another thought - they might be cousins, as families often named all the kids after fathers, and grandfathers????