Mildred, There is a MOSES HARRIS on the 1800 census of Pendleton District (or is it county by then) in SC. However, the age code certainly does not agree with him having 12 children. His age code was 000100-01100 which would indicate 1 male about 35 years old, his wife and one daughter about 10-15 years old. Seems to be a few children missing. Moses is on page 130 of that census. There is also a Martha on page 129 who apparently has 8 children under the age of 16. Interesting that Martha is about age 35, there is a male in the house, also about age 35, yet Martha is listed as the Head of Household. That is unusual for the times.
There are 11 more Harris families listed on that census.