I found very little about this family on Ancestry and FamilySearch.
1900 Oil City, Venango, PA
Margaret Morrisy, b. Ireland, 1825, widow, 7/7 ch
Demis, b. Canada-Eng, June 1864
John, b. Canada-Eng, April 1863
Philip, b. PA May 1870
James, b. PA, 26
I did find your family tree and see that you have many gaps in info. I'd order all of their obituaries where you've already found their death dates. You also might hae to order copies of death certificates.
Venango county didn't start to register deaths until 1893. Those records are at the PA Archives, www.phmc.state.pa.us./bah/dam/rg/rg47m.htm
. They also have wills 1800-1969
The Venango County Genealogical Club, http://vengen.org/index.php/resources
has Oil City Directories 1887-1898 and county directories, church, cemetery and other records.
Heritage Society of OIl City, pennsylvania, www.facebook.com/
The Venango County Historical Society, www.venangocountyhistory.org/
has wills 1800-1900; estate files 1800-1900, naturalization files 1800-1900, family records, newspapers, etc. Successful Searching!