Blenkhorn, David (1803) - Searching for his parents

I found this information below in an earlier post to this group and am very interested in finding this David's parents (his granddaughter Bessie is my great-great-grandmother).

I've seen references to Robert T. Blenkhorn and Margaret / Martha Mills; however, they weren't married until 1811 (and mom would have been 13 years old in 1803).

Any information you can provide (or direction as to where to look) would be very much appreciated.

Buried at Pereau Cemetery, Kings County, all on the same headstone.
David Blenkhorn, died 8 April 1860, age 57
his wife, Ester, died 8 August 1890, age 86.
Bertha, died 15 Nov 1955, age 82
D.L., 1877 - 1938
Mrs. Rheuben Blenkhorn, buried 18 Nov 1956.