A Lewis Pease was also listed in the church records - but a brief online bio of the man indicates he was not the father of my new mystery: Marie Pease.
It was only recently that I found a record identifying the mother of John Hempstead as Marie Pease [per NY Town Clerk Register of Men Who Served in the Civil War, ca 1861-1865]. John, born 1828, was the second child of Christopher Hempstead Jr. He had an older brother, Christopher III who died at a fairly young age in upstate NY; nothing much found on him to date. Their sister Phoebe Hempstead was born 1830; her death certificate lists her mother as Alice Smith.
Family history has it that my mother, Gloria Marie, was named [partly] for her grandmother, Alice Marie Morrell, daughter of Phoebe Hempstead and Adrian Morrell. Alice, in turn, was named for her grandmother, Alice Smith. The repetition of the names Alice and Marie in the family lead me to believe that the secondary info provided in that death certificate was correct. However - I wonder if Alice Smith and Marie Pease could be the same person: Alice Marie Smith or Pease.
Chris III, John and Phoebe Hempstead were born 2 years apart, or very close to it. [Don't have exact birthdate for Chris III.] The censuses aren't very helpful, as Chris Jr. wasn't married at 1820; at 1830 his spouse was a female born 1800-1810; and at 1840 the spouse was a female born 1810-1820. However, church records at 1837 list a different [his second] wife for Chris Jr.: Elizabeth. Thus it is she appearing in the 1840 census, with Alice only appearing in 1830. Since Phoebe was born 1830 of Alice and Chris, I must assume the spouse in the 1830 census was Alice, and that she died before 1837. However, this gives me no information on whether or not Chris Jr. had a spouse prior to Alice, possibly a Marie Pease who was the mother of John and, presumably, Chris III.