I'm not related and I did not find much online but perhaps this will help a little:
David E. Keller married Eliza Dickenson (Dickinson) 8 Nov 1877 in Fairfield, OH. Looks like they had three children before they died in 1882:
1. Emma Keller was born 23 Sep 1878 in Truro Township, Franklin Co. OH
2. Nellie Naomi Keller was born 1 Mar 1880 in Latty, Paulding Co. OH
She married William S. Campbell 28 Feb 1924 Franklin Co. OH
3. Hattie Victoria Keller was born 20 Oct 1881 in Latty, Paulding Co. OH
It does seem odd that both David and Eliza died in 1882 (both at a relatively young age). It will be very difficult to find a cause of death that occurred so long ago unless you can connect with a descendant who know the family history.