I have seen the census data that I think your refering to. I have also seen two explainations for this data, and frankly I don't have any hard proof as to which is correct, though one appears more likely as you may or may not agree.
I have the two possibilities as follows: Thomas W. Gulledge b. 1821 in NC spouse Elizabeth b. 1830 married abt 1852 with children: Mary b. 1855 Daniel b. 1860 Nancyb. 1865 Presley b. 1867 Jefferson D. b. 1870 This Thomas W. is listed as son of Joel Gulledge Jr. and Sarah Elizabeth Sellers of Anson NC.
Thomas Gulledge b. abt 1810 in Chesterfield Co. SC spouse Elizabeth Wallace b abt 1820 in SC with children: Alexanderb. 1837 Sarah Annb. 1844 Mary Janeb. 1845 Catherineb. 1847 Samuel Edwardb. 1850 John P.b. 1852 Margaret E.b. 1854 Daniel G.b. 1860 Thomas P. b. aft 1860 Nancy E. b. 1865 Anzillab. 2 Oct 1867 William Jeffersonb. 1870 This Thomas is reported as son of Edward Gulledge II (Edward of Bladen) and Alice Walter both born abt 1710. Note the date of Edward and Thomas make it impossible for this to be completely accurate.
My belief is that someone has either mixed up two families, or possibly duplicated a single family, with different children details known (but same family) under multiple parentage lines. Clearly Edward II did not father Thomas when 100 years old, but since the dates are estimates, that does not rule out that the ancestry could be correct. It seems well documented that Edward II had a son Thomas. According to Marrie Wiggins, this Thomas went to Pike County Mississippi, not South Carolina.
For this reason I lean to Thomas as being son of Joel. My difficluty then arises as in what to do with the children detail that is under the Mississippi Thomas as it appears that someone had additional data on the same family but put it on the wrong Thomas. I do not know for sure if Anzilla is a sibbling to Presley as you mentioned. I do believe that someone believed that the John P. on the MS Thomas is the same person as the Presley listed for the S.C. Thomas, but note the difference in the dates.
My best guess is that the Five children shown on the 1880 SC census were added incorectly with the children of the Mississippi Thomas, noting the close resemblance in dates for Mary and John P. and the complete match for Nancy and Jefferson (though Jefferson's name is not a perfect match).
I don't have copies of the reported Pike County information that details the Mississippi Thomas, so I can't tell you what matches or doesn't. But I can say since Anzilla is reported born in 1870, and doesn't show up on the 1880 SC census, it appears to me that they are not siblings.