The 1850 census for Marlborough, Ulster, NYhas David with wife Sarah.
Both are shown born NY in this one.
David, 64 born NY
Sarah, 63 born Ny
Do you know when and where David died? I ask because in 1870 census there is a David Merritt, age 86, born NY - but living in Westchester Co. NY
he is with the family of Joel F. Gilbert 62, J. Gilbert 53, Catharine,a ge 11, and Benjamin, age 6
could J. be daughter of David?
I also notice in the 1800 census there is a David Merrit in Marlborough, Ulster and the family consists of
MALES 1 age 10-15, 1 age 45+
FEMALES 2 age 10-15, 1 age 26-44
so possibly the parents and siblings of your David as if he was born about 1784 , then in 1800 he would be about 16 so may have fit in the 10-15 age category - it is close enough to fit if so, then his father was also named David as that is the name of the Head of the household
1790 NY census also has David Merrit in New Marloborough, Ulster
this census only asks for number of free white persons male age 16 and over - 2 free white person females - 4 number of slaves - 1
total - 7
so no number of males under 16 shown and does not say what the age spread is for the females