This certainly is interesting, and there must be a connection.
The name Sarah Jane Whitley as the wife of Hugh Allen (b.1745) came from someone else, and may have been the name of someone in the next generation of Allens or simply a mistake.At any rate, it does indicate that someone believes or believed your William Allen (b. 1783), who named a son Whitley, might be of this branch.
Do you know who William's wife was, and could she have been a Whitley?
I suggest contacting Tom Myers, who knows more about the Allens than anyone I know.He's posted messages on this forum.You might also ask Libby Freeman.
This appears to be the correct list of Malcolm Allen's children:
David Allane's son Malcolm Allen married Mary Dean on June 14, 1699 in Scotland.Their son Malcom Allen, born April 27, 1712 in Kilbirnie, County Ayr, Scotland, died January, 1792 in Botetourt County, Va.
Malcom married Mary (Hughes?) about 1739. (born about 1719?).
Their children (from John Allen's bible) were:
Rebecca b. May 29, 1740
Mary b. November 10, 1741
Martha b. November 19, 1743
Hugh b. September 4, 1745
Robert b. November 26, 1748
Moses b. October 9, 1750
Elizabeth b. October 9, 1750
Leley b. March 12, 1753 (thought to be Scotch spelling of Lilly)
John b. August 17, 1759.
There never was a Malcolm, Jr.Hugh's son Malcolm was referred to as Malcolm, Jr. to distinguish him from his grandfather for legal reasons only. His grandfather signed his name on occasion "Malcom Allen, Sr."
Rebecca married Caleb Worley in 1758. They had children: Mary, David, Malcham, Caleb, Ann, William, Moses, Nathan, Rebecca, Martha, Joshua, Rachel and Polly.
Mary married John Mc/Clure, Sr.about 1756. They had children:Hannah, Jane T., Malcolm, Nathaniel, Rebecca, Agnes, John, Halbert and Moses.
Martha married Henry Caldwell on August 7, 1766. They had children: Polly and George, and possibly others.
Hugh married Anna Hunter on November 6, 1765. They had children:Robert, Anne, Jane, Malcolm "Jr" (m. Margaret Henderson), Thomas, William, John, James, Betty, Matilda, Polly (probably Mary who married John Birdwell), Patsy, Rebecca and Moses b. c1783.
Robert married Jane Hill on March 20, 1784. They had at least one child. Name unknown.
Moses married Lydia, date unknown. They had children:Rebecca, Jane, John, Malcolm and Polly.
John married Rebecca Poage on April 22, 1785. They had children:Mary, Martha, Sarah, James S. Elizabeth, Harriet, John Franklin, Jefferson, Rebekah and Madison.
Nothing is known about the marriages, if any, of Elizabeth and Leley.
Malcolm, son of Hugh, married Margaret Henderson, daughter of John Henderson and Mary, January 7, 1794 in Botetourt County, She born about 1773 and died 1826.
They had children:John, Joseph, Archibald, William, Mary Ann, Newton, Elizabeth, Cary and James.