I just located in the Census of 1850 for Guilford County, a William Wrenn age 70 who is listed as a pauper in the Poor House of Guilford County, NC. He gave his birthplace as Person County, North Carolina. This may be the William Wrenn who married Nancy Mann in Person County 14 December 1809. His birthyear would have been ca 1780. The only problem with this is the fact that Person County was not formed until 1794 from Caswell County, NC.
In the same census is a Rebecca Wrenn age 30 listed as head of household, with a son age 4, John A. Wrenn. I do not know if this Wrenn attaches in anyway to the William above.
Further along in the census is a family of Henry Wrenn, age 28, wife Margaret, age 28, children, John W. R. Wrenn age 4; and Mary I. Wrenn age 2. Henry listed his birthplace as Person County; which does seem to tie him to the elder William Wrenn, at least with an in-common place of birth.
Another Wrenn found was Martha J. Wrenn age 16 found in the household of Gofisia Wyrick age 78 and a John Wyrick, age 27.
Another listing is James Wrenn, born in Person County, age 31; Mary Wrenn age 36;children, Henry Wrenn age 8; Peter Wrenn age 3; Margaret E. Wrenn age 3.
Another single Wrenn, is Madison Wrenn age 14, born in Guilford, in the household of John Chrisman, born in Guilford, age 78; and Maryan Heritage, born in Caswell County NC, age 34
All of the above Wrenns were located in the Northern Division of Guilford County, NC