Nancy Hanks' lineage

[STS Lincolnite]

In the context of this sort of the Lincoln/Hanks family history study, and what has been posted here, what exactly is the definition of "illegitimate"? Does it mean born out of wedlock? Does it mean the name of the father is unknown? Is it a combination of the two?

To me illegitimate simply means born outside of wedlock. Having an unknown father is another issue. It is still possible to be an illegitimate child of a known father. There could also be a legitimate child with an unknown father (where a mother is married, has a child with her husband, but there is no extant documentation to definitively show who her husband was).

I am trying to clarify in my mind, so I have starting point to work from when reading about the "gnarled" lineage of Nancy Hanks Lincoln.

My understanding of the most current conclusions, after having given this information a cursory read through, is:

1) Nancy Hanks Lincoln (mother of Abraham Lincoln) is the daughter of Lucy Hanks Sparrow. Nancy is an illegitimate daughter whose father is unknown.

2) Lucy Hanks Sparrow (Abraham Lincoln's maternal grandmother) is the daughter of Ann "Nancy" Lee and Joseph Hanks. She was the mother of Nancy Hanks Lincoln and Sarah "Sally" Hanks, both of whom were born out of wedlock. She later married Henry Sparrow and had additional children.

A couple of questions. Is there proof that directly corroborates or indicates (extant primary documentation) that Nancy Hanks Lincoln and Sarah "Sally" Hanks were full biological sisters and not half-sisters? Is it possible (both apparently being illegitimate), that they had different fathers?

That probably muddies the water even more.

It seems to me that there can be no definitive answers to many of the questions of Lincoln's maternal ancestry when comparison DNA of a confirmed descendant of Nancy Hanks Lincoln is lacking.