Pardon the slightly belated follow-up, but I don't check this message base on a daily basis. I tried to send to your email address, but for some reason it would not go.
While this is not my direct line, nevertheless my database has Joel identified as William Joel Abernathy. His wife's full name was evidently Margaret Melvina 'Viney' Allison. I have 10 children listed for this couple, with birth dates on most and death dates on all but 2. I have nothing on Martha (your line, I believe) and would be pleased to add it to my database.
I find Joel in the following post-1840 census records: 1850 Habersham Co, GA; 1860 White Co, GA; 1870 White Co, GA; 1880 White Co, GA. I also believe him to be included in the tally marks for Buckner Abernathy on the 1830 and 1840 Habersham County GA census data.
Unless I am mistaken, Joel's date of birth is the same as that of James, son of Robert Buckner and Mary Jane Abernathy (I do not know her maiden name) inidicating that Joel is twin to James, so that while I do not have documentary proof, merely strong circumstantial evidence, it appears that he is a son of Robert Buckner and Mary Jane Abernathy. If this is, indeed, true, then Joel's siblings include the Robert A. Abernathy and the V.A. Abernathy found on the 1850 Habersham County census in the household of Robert Buckner and Mary Jane. The list of siblings may also include Milly who evidently married James Allison, Miles who evidently married Margaret Westmoreland, plus two as-yet-unidentified sons who may have died young.I have no data on the parentage of Robert Buckner Abernathy (b. abt 1783 in VA, d. 187? in GA), since Virginia records are few and far between, and there are all too many Abernathys found in VA and NC just prior to and immediately after the Revolutionary War.
Of the children of Joel and Viney Abernathy which you lacked data, here is what I have:
Lucy is said to have married Harvey Adams. She is said to have been born 3 Jul 1858 and d. 24 Nov 1922, but I lack cemetery records to fully substantiate this data.
Henry, married Emely [sic] L. Westmoreland 10 Jan 1883 in White Co, GA [IGI Extracted records]. Henry's birth has been given as 11 Jun 1863 and death 5 Sep 1936. His full name has also been given as Henry Newton Abernathy. I lack cemetery records to substantiate this data, but have no reason to doubt the veracity of the data.
Amanda's full name is said to be Amanda Maud Abernathy. She is said to have married William Robert Westmoreland. Her birth/death dates are said to be 9 Jul 1860 (White Co, GA) and 1 Jun 19.3 (Hall Co, GA) but again, I lack cemetery records.
Benjamin married Eva Ida Crumley on 4 Jan 1891 in White Co, GA [IGI Extracted Marriages]. His full name is said to be Benjamin Hill Abernathy, and his birth/dates are said to be 5 Oct 1865 and 12 Apr 1937, both in White County, GA. Her birth/death dates are said to be 13 Apr 1874 and 7 Apr 1960, probably also White County. Again, I lack burial records and would love someone to send me a reference where I can find that data.
Julia's 1880 census data indicates birth abt 1870 in White Co, GA and I believe she married D. W. Price abt 1889. I do not know what her middle initial stood for, nor her exact birth/death dates.
Alice, so I believe, was Olive Alice (or Almar) Abernathy and married Almon Elisha Ledford on 29 Jul 1888 in White Co, GA [IGI Extracted Marriages]. I believe that he is said to have been born 21 May 1867, son of Thomas L. Ledford and Nancy A. Johnson, but have not researched for documentation as yet. If Olive is also Alice, then the birth/death dates I have are 14 Apr 1868 (White Co, GA) and 27 Jul 1917 in Maysville, GA. Maysville apparently sits astride the county line seperating Banks County GA from Jackson County. I have no cemetery data.
Other known and documentable children of Joel and Viney include:
Coleman A., who is said to have died 24 Jan 1863; William Jasper, who married Ceceila Westmoreland and had at least 3 children); Martha, who is said to have died 7 May 1921; and Mary Caroline, who married J. Floyd Collier on 5 Jun 1873 [IGI Extracted Records].