I don't know how others will react, but I find it offensive to refer to Sally Hemmings as a "sex slave."
They had sex and she was a slave. Her choices were... limited. You may find it offensive, but that doesn't keep it from being true...
It seems to me that our modern-day term "sex slave" is an attempt to say that a relationship between X and Y is like the relationship between... Thomas Jefferson and Sally Hemings.
I think that William Freehling got it right (writing long before DNA testing) in his Secessionists at Bay, pp. 128-9:
One episode at Monticello illustrates the master's [Jefferson's] genius at evasion. Sally Hemings, Monticello's most celebrated slave, put Jefferson to the test as few trustees have been tested. No trustee more successfully evaded his examination. Most historians, emulating Jefferson's contemporaries, have narrowed the Sally Hemings issue to one question: Did Jefferson sire her five mulatto children?
The circumstantial evidence does not serve Jefferson well. Hemings, whitish daughter of Jefferson's father-in-law, was long a household servant within the Big House. Jefferson was always in residence nine months before she gave birth. Jefferson manumitted some of her children and freed no black without a Hemings connection.
This evidence, to some, will always convict Jefferson. Others will urge that these circumstances could point towards other member(s) of Jefferson's white family as sire(s). Furthermore, the fact (at last a fact!) that Jefferson's father-in-law sired Sally Hemings perhaps explains why only Hemingses were manumitted.
This futile debate over circumstances obscures the undebatable point about dissimulation. Jefferson never faced or resolved the moral mess in his mansion.... And morass miscegenation was, as Jefferson defined morass, the most 'unnatural' morass infecting the 'natural aristocracy'.
As Jefferson knew, miscegenation, however common in the Old South, was not commonly that luxuriant in southern Big Houses. Multiplying mulattoes were also uncommonly 'obscence' in so uncommon a mansion as Monticello. This was supposed to be the utopian Big House, the model on the mountain for an adoring South to emulate. A morally enlightened trustee would have had to act, however unpleasant the action...
Jefferson preferred to avoid the unpleasant.... Jefferson chose to do nothing. Or, more accurately, he probably never allowed himself to think about the choices.... Jefferson's love of balanced surfaces and inclinations to forget unbalanced foundations explain why he failed almost as much as manumitter as he failed as Sally Hemings's trustee. That 'almost' is crucial. Jefferson freed some 10% of his over 100 slaves. 10% per generation could water down slavery. So, too, Jefferson's voluntary surrender of 10% of his property shows some commitment. Latter-day intellectuals who can see only commitment to slavery might ask themselves how often they have sacrificed 10% for their ideas.