The book James T. Martin, Anson County, NC: his ancestors and descendants, by John Ratcliffe, Winter Park FL 1985, lists a Coleman Allen as the son of Young Allen and Nancy Coleman. (ch. 19, p 199) says Young Allen lived and died in Wake County NC and his will is recorded in Wake County, Book A, p. 52 on Feb. 7 1775. I have no further info on Coleman, my line comes through his brother David m. Nancy Dawson. I haven't seen the original will or even a transcript of it.
It is possible is that Young Allen is also known as William Allen with a will listed in Wake County, NC on Oct. 29, 1774. I have no firm proof of this, simply references that I have found on the net, and I haven't seen the full text of the William Allen will, though the children listed are the same as in the above book [the reference to this will is on afrigeneas, and primarily concerned with the slaves held by William Allen, the children are listed as an aside].
I have seen hints that Young Allen might have been the son of Robert Allen Jr (b. abt 1704 in New Kent County, VA, d. 1784 in Caswell County, NC) and Elizabeth Young m. around 1725 in Virginia. This was on someone's family tree with no sources listed, so take it for what it is worth--a potential lead and no more.