This is also consistent with the 1780 birth year arrived at for Mary Wilson, wife of Thomas Gill. Perhaps Thomas and Mary Gill lied about their ages for some reason. Julia May Gill Peebles was caught in such a trap, lying about her age to get a job, then having to work past her retirement age. In all likelihood, he was older than she. Written records to clarify the children beyond what is listed here may be difficult to find, but try nonetheless.
Earlier children are possible.
The three sons, James, Thomas, and Robert fit the set listed in the Creek Nation passport. Thomas Gill and Robert Gill, at least, obviously came back, or never left. I assume he resided with his mother. I emphasize again that only Thomas Gill and John Nielson Gill are documented. The census records a son of John Gill born c1773-82.