I've linked Nancy, the wife of Samuel Miller, into this family as "Nancy Gray" based upon the following facts:

1. The 1840 census enumeration of a Samuel Miller in the middle of the Gray family
2. The above census has 3 females, aged 0-9, as the only children of that family.
3. The 1850 census for the Miller family has the eldest daughter named "Rachel."
4. The 1850 census for the Miller family has 3 daughters over age 10, and no sons over age 10.
5. The ages for Samuel & Nancy Miller fit perfectly into both the Gray family and the 1840 census.
6. In the 1850 census records for Georgia, Flordia, and Alabama, there aren't any other good
matches for the above set of facts.

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This family is enumerated (on Line 3 of Images 5-6 for District 95) in 1840 as:

1 M (10-14), Zachariah Gray (age about 13)
1 M (50-59), Enoch Gray (age 55-56)
1 F (15-19)
1 F (20-29), Elizabeth Gray (age about 24)
1 F (50-59), Rachel (Sparks) Gray (age 55-56)
==== SLAVES ====
2 M (10-23)
2 M (24-35)
2 M (55-99)
1 F (0-9)
1 F (10-23)
1 F (36-54)

Note that the family of son William Gray is on Line 1 of this same page, two lines up the page. So, is the intervening family (of Samuel Miller on Line 2 of that same page) also related? Did "Samuel Miller" marry one of Enoch Gray's daughters? The age of Samuel's wife is a match, and I've found a "Samuel Miller" family in the 1850 census that is a match for that 1840 census record and the oldest daughter is named "Rachel," so I'm linking all this together.

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This family is enumerated (on Line 5 of Images 61-62) in 1830 as:

1 M (0-4), Zachariah Gray (age about 3)
1 M (10-14), James Gray (age about 10+)
1 M (20-29), William Gray (age about 20)
1 M (40-49), Enoch Gray (age 45-46)
1 F (5-9)
2 F (15-19), Nancy Gray (age about 18) & Elizabeth Gray (age about 14)
1 F (20-29)
1 F (30-39), Rachel (Sparks) Gray (age 45-46, so one notch too young)
==== SLAVES ====
2 M (0-9)
1 M (10-23)
1 M (36-54)
1 F (0-9)
1 F (36-54)

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This family is enumerated (on Line 11 of Image 9) in 1820 as:

2 M (0-9), James & who?
1 M (10-15), William
1 M (26-44), Enoch Gray (age 35-36)
3 F (0-9), Nancy, Elizabeth & who?
1 F (26-44), Rachel (Sparks) Gray
==== SLAVES ====
1 M (14-25)

Enoch's family is the middle family of three: Sarah Sparks (widow of Benjamin), Enoch Gray (husband of Rachel Sparks), and John Sparks (patriarch of the Sparks clan of Washington County).