Bob, I have Cyrus in my data files. I have his birth as about 1733, but I have a source for his death as 26 Feb 1802. The source for my information is: Margaret R. Jenks, Poultney Cemetery Inscriptions Rutland County Vermont (n.p.: n. pub., 1996), p. 11.
I have Cyrus as the son of Phillip and Sarah Keyes. What is your source on date of death?
Unfortunately, I do not have any information on his wives or children.