In both deeds, a slave woman named Letty is listed as additional collateral.
William F. Read appears in the 1830 US Census in Fauquier County, Virginia. The record shows him with two boys under the age of 5 (Rice and Guilford), one between 5 and 10 (unknown), himself (31 years old), a daughter between 5 and 10, and his wife Emily (28).
In this census record, William also had three slaves, one man between the ages of 10 and 24, a child under the age of 10, and a woman between the ages of 10 and 24. Perhaps this was a young family. I don't know if Letty in the 1841 and 1844 deeds was the same woman from the 1830 Census.
I have not been able to find William and family in the 1840 Census in Fauquier or Culpeper Counties. By 1850, William and family were in Barren County, Kentucky, and did not own any slaves.