Thanks for speedy reply, Dan. I do see now that George Allen m. Nancy Carlisle 24 Dec 1835 (Ref: Fairfield Co. OH Marriage Records - LDS Film #0317372)She's dau of Thomas Carlisle & Sarah Ann Edwards who were m. 23 Jan 1813 Lancaster Twp. Fairfield Co., OH. Thomas & Sarah Carlisle also named a son Thomas Jefferson Carlisle.
Now, looking at the 1840 census: 1840 Census - Fairfield Co., OH pg. 295Greenfield Twp Thomas Carlisle . . . 001110010 - 00120001 pg. 296Greenfield Twp . . . George Allen. . .101010001- 1000100160-70 pg. 270 Lancaster Twp . . . George Carlisle . . . 00000100 - 120001
Obviously the above George Allen is too old to be our guy, but I think George b. 1810-1811 was George Jr. the 20-30 year old male in the above household and the under 5 children belong to George Jr the 20-30 male here - the under 5 female is your Sarah b. 1837 and the male child under 5 would fill the gap in ages of known children of George & Nancy Allen on the 1850 census.
Also, I suspect the only way to find out what was going on with George and Nancy & their move from Fairfield Co., OH to Shelby Co., IL and then his return to Ohio is to look at events of the time period - the Civil War.Or . . . possibly the land records might reveal George may have had land transactions in Fairfield yet to be finalized and returned to deal with that once he had his family settled in Shelby Co., IL.He possibly fully intended to return to Illinois, but fate intervened.
This is not my own family.I work on our neighborhood families - we're all connected in some way we're finding out. I'll keep nosing around on this and if anything else turns up I'll pass it along.Check Worldconnect.