According to Jacobus in The American Genealogist. New Haven, CT: D. L. Jacobus, 1937-. (Online database. AmericanAncestors.org. New England Historic Genealogical Society, 2009 - .)
https://www.americanancestors.org/DB283/i/11884/183/23574198
The parentage of Mary wife of John Spencer is unknown. Through a merge Mary has become the daughter of "Gov" Benjamin Miller (1672-1747). The profile does not appear to give documentation for the children listed or the statement a daughter Mary married a Mr Spencer of Haddam. If she did marry a Mr Spencer of Haddam, what documentation shows that it is John Spencer? Jacobus was aware of the families and did not make this connection. There is a second profile for daughter Mary attached to Benjamin Miller and she is there married to an Unknown Spencer.
I am suspicious of the connection being made here as this then links all descendants of John Spencer to George Washington. Great if this could be documented but it does not appear to be documented at this time. Can some of our Connecticut specialists have a look at this? Thanks.