I just thought I'd contribute a little bit since I know something about all this.
My great-grandfather is Daniel Lavender Slaton, son of Augustus Marion. I worked with Becky Heaney back in the 70s, in fact we took three days to exchange information. She was on the move even back then and I don't know where to contact her. I do recall she had a sister and brother-in-law living in Utah, but I don't remember their names. They were descendants of Sarah "Sallie" Slaton, younger sister of Daniel, by Sallie and her husband, James Elijah Portis.
"E.M." on the census is Sallie's son by the hired man, Joseph Litchfield, confirmed by the wife of Henry Clay Slaton (descendant of Zachariah Slaton, Daniel's brother) who I interviewed many years ago in Brandon, MS. Later Becky told me that she had tracked E. M. to Holmes County (or possibly Sunflower Co.) and he had been raised by friends or relatives. Some years after the birth of her child, Sallie married Portis in Yazoo Co. and moved to near Crowley, LA where Sallie died. Portis then remarried twice more and had many children. Unfortunately I don't remember if Becky ever determined what "E.M." stood for, and of course it could actually be "M.E.", knowing census takers like we do. Joseph Litchfield later married Mollie King and is buried near the Slatons in the Hicks or Medley Cemetery in Yazoo Co.
Litchfield came to live on the Slaton place in Kemper Co., MS from Ala. after the WBTS and I believe the pregnancy was the was the reason Sarah and her children Zach, Dan and Sallie moved to Yazoo Co. in 1879. Augustus' two older sons, John Thomas and James William Slaton, had married Kemper Co. girls by this time and stayed in Kemper Co. One other child of Augustus and Sarah, Margaret, died as an 8-year-old and I presume is buried either on the Kemper Co. Slaton farm or at Union United Methodist Church in Kemper Co. where Augustus Marion Slaton is buried. Sarah Sloan Slaton was buried in the Hicks (or Medley) cemetery in Yazoo Co. near the tiny community of Nod, where my grandfather, Henry Clay Slaton (son of Daniel Lavender Slaton) was born.
BTW, Daniel and Ailsey were living apart on that census because Ailsey was home visiting her family when the census taker came around. They eventually had 10 children and they are buried side-by-side in the town cemetery in Petal, Forest Co., MS.
I hope very much this helps. If anyone has other questions, I'll be glad to work with you via e-mail as best I can. firstname.lastname@example.org