> If this is Isaiah's wife, where was she in 1840?
Good question. For which I have no answer.
> Elijah had a daughter named Lucinda who married a John Abernathy. Do you think this could be the son of Isaiah?
I have what might be Isaiah's son John married to Mary Polly Farewell on4 Nov 1840 in Lincoln County NC [src, Bynum, p. 9]. It might be possible that I have the wrong John assigned to Isaiah and Sally, I can't say for sure, but Isaiah stood as bondsman and both John and Isaiah signed the bond with an X. This follows a pattern consistent with all the rest Isaiah's appearance on marriage bonds in Lincoln County, and the age of John fits reasonably well also.
> Do you known where Lawson Abernathy fits in? He is listed in Wayne Co, MO, in the 1840 census near Elijah.
I believe that Lawson Abernathy returned to Lincoln County with his wife and children, was on the 1850 Catawba census, and then moved to Iredell, where I believe that he died before 1900. I have a death date for him, but no source for it and no confirmation on burial location as yet. I feel sure there are databases out there that assign him to one of the many Abernathy families around at the timey, but I am getting to a point where I am deeply suspicious about the vericity of the vast majority of them.
> Do you know the source for listing Isaiah as being born in 1792, and where does the list of children come from?
The short answer is "tradition".. I know of no one that gives any source for Isaiah's birth year, nor for the list of children. This is a common problem with trying to identify children before the census records started listing the names of all in a family. However, there is some consistency between the 1820 and the 1830 Lincoln County census listings as regards the ages of Isaiah, Sally, and his children (6 sons, 4 daughters). These two census records tend to support a birth year for both Isaiah and Sally between 1780 and 1790, instead of later. But then a question arises arises concerning that 1840 census listing: it shows Isaiah as 10 years too young and no wife, leaving aside the question of the children and how they fit. Is this the same Isaiah and the census enumerator goofed? It's been known to happen. Is that why Sarah isn't tallied? In all honesty, I don't know, but this is the only Isaiah I have in my database until Hardaway and Evaline McCormack Abernathy of Giles County TN gave that name to one of their sons that 1827. Isaiah isn't a very common given name amongst these folk as are several others.
> If the 1840 census listing is the correct Isaiah, there could be as many as 12 children listed in that household, but only four are > commonly listed in the internet postings
I know. I am afraid that I have to opt for a minimum of 10 children: 6 boys and 4 girls. Most just waiting for identification. Now, granted, some could have died in an epidemic before the 1850 census. There was one about 1847 that wiped out half of the boys from one Abernathy family alone, from which the family had a hard time recovering.
I don't know if any of this has been of any help for your purposes, but I did my best.