J. Louisa and Sara T. Hitchcock

A list of Harrington and Clement births and deaths includes entries for:

I don't know who these people are. Random details I've found:

The 1892 New York Census lists J. Louisa aged 54 and Sarah T aged 18 living in Cambridge, NY. Their entries are adjacent to Daniel Harrington (1834-1917) and family, which might or might not be significant.
J. Louisa's probate record shows that she lived in Cambridge but the administrators aren't anyone I know of.
The 1900 US Census says that Louisa Hitchcock lived on South Union St in Cambridge, which would make her a neighbor of the Harringtons there.
Find a Grave has William McClay's grave, showing dates of August 1848 - May 2 1918, died in Cambridge.
Various record such as the 1880 US Census show McClay living in Washington County. There's no indication of being related to the Harringtons so he was probably another friend or neighbor.