Did you every get an answer as to who was Homer Cheney? I think I have an answer.
The index of Michigan marriages (1851-1875) shows a Charles Cheney married to Charlotte Graves, 14 Feb 1863, in Jackson County. I believe this is Homer's parents. Charlotte was the daughter of Martin Graves and Mary Ann Douglas. The people Homer is living with in 1880, although he is shown as an adopted son, are his three uncles and his maternal grandmother.
I don't know the Ryan family he is living with in 1870 but the Graves family that is listed next in the census is his maternal grandparents and two of the uncles he is later living with in 1880. My guess would be the Ryans are an aunt and uncle on the Cheney side of the family.
If I am right, it would indicate that Homer's parents both died between the time he was born and the 1870 census.
I don't have any hard evidence to support my theory, but it is a place to start. The Graves family moved to Michigan circa 1840 from Crawford County, Pa. My wife can trace her family back to Martin Graves' parents.