Re: James Cooke (1865 New York) and Mary E Kelly (1869 Pennsylvania)
I suggest getting their death certificates. In NY I understand it is best to go to the town or city clerk to get them. You might also try to get their obituaries. Check with the New York Public Library or perhaps a historical or genealogical organization local to Brooklyn since their obits were more likely to appear in a newspaper from Brooklyn rather than say the New York Times. You could also call the cemetery where they are buried to see what they have in their records on them. If you know what church they were members of (which might appear on their obits) contact the church to see what is in their records.