Dexter's parents were Ephraim Kasson and Maria Noonan. They were from Broadalbin, New York, which is in Fulton County. Eprhraim was the son of Robert Kasson and Polly Brockway. Robert was the son of Robert Kasson (who served in the French & Indian war, and the Revolutionary war) and Janet (Jennie) Gaston. They were originally from Connecticut, and settled in Broadalbin after the revolution.
Here is a site where you can get some information on the the Brockway's: http://library.syr.edu/digital/guides/b/brockway_fam.htm