According to the 1900 census where he is enumerated with the Turnley famiy in Deerfield, Illinois, Milton Turnley Lightner was born in October of 1880.Then on his WWI Draft Registration card, filled out in Colorado, he is more specific and says he was born Oct 28, 1880. So, using 9 months as an average pregnancy, if his father died in 1880, but after 1 February 1880, then he most certainly could still be his father.If Edwin Nathaniel Lightner died in the first couple of weeks of January, maybe not, but certainly still possible if his wife's pregnancy was overdue.
The only fly in the ointment is that Milton Clarkson Lightner, episcopal minister, who can be found in the 1850 and 1860 Reading, Berks, Pa censuses and in the 1870 Detroit, Michigan census lists as his wife in all 3 censuses, Martha H., born in Pa abt 1825.Martha would have been aged 55 when she gave birth to Milton if she had been his mother, possible but somehow kind of doubtful.The father of this Milton C. Lightner, who has quite a well-documented tree was Nathaniel Ferree Lightner.
Looking through the censuses, I also found:
1850 and 1860 Chicago censuses with Dr. David and Esther Rutter with single daughter Mary R.(aged 14 in 1850) and married daughter Mary Turnley(aged 24 in the 1860).About 1853 daughter Mary Rutter married P. T. Turnley who was born in Tennessee in Sep 1821 according to the 1900 census.They had 5 children, only 2 of whom were still alive in 1900 (Emma and Ethel), daughter Mary(born abt 1858 in either Pa or Ill depending on which census you believe) and son Ernest (born in Illinois in the 1870's) both died before 1900.The daughter named Mary who was born abt 1858 is not with her parents in the 1880 census - this is your Milton Turnley Lightner's mother who must have died before 1900 which is why Milton Jr is with his Turnley grandparents in 1900 and 1910.If so, I suspect that she is the M.T. (for Mary Turnley - the wife's initial was usually the initial of her maiden name, not a middle name) Leitner in the 1880 Chicago census, her husband being M.C. Leitner, aged 29, born in Pa, so born abt 1851)of Pa-born parents (In this census Mary again says she was born in Illinois which seems most logical as there is no evidence that her mother went to Pa to have the one child).There is no Milton Leitner in the 1870 census who would remotely fit this M.C. Leitner, but given that Milton Jr is always spelled Lightner, I would guess the Leitner is an error on the part of the censustaker.There is a 19-yr-old Milton Lightner in the Mount Pleasant, Racine, Wisconsin census and he was born in Pa. and is attending school (where he was enumerated).
So at least you can knock off the Rev. Milton Clarkson Lightner as the father of your Milton as both he was in Michigan when he died in 1880 and it seems quite logical (because it all fits together) that M.C. and M.T Leitner are your Milton's parents and that M.C. Leitner/Lightner was born abt 30 years after the good reverend.
If I were you, I'd check out Lightner/Leitner marriages and births in the 1879/1880 range and a Mary Lightner/Leitner death (and maybe M.C. too) sometime between 1880 and 1900 - and just in the Chicago, Cook county, Illinois area as that is obviously where the marriage and the birth took place for sure - I would suspect that your Milton was the first and perhaps the only born child to this couple.
Good luck and if I can help in any way, let me know - I love a good mystery!