Search technique used.When you can't find the people you want look for relatives.
First located your family on the 1880 US census, which is how I suspect you came to the conclusion that Warren was in Michigan by 1870, since he had children born there just before and after 1870.
I searched for Warren's family in Michigan in 1870 but didn't find them.So, I checked to see if there were Fisher's in the Grand Traverse county in 1870, because that was where Warren was in 1880.The 1880 census had a couple of other clues.Warren had a son named James Jr.Hmm.Who was James Sr?Maybe Warren's father?Also, Warren's mother was shown as born in VT.
I found a James Fisher, wife Emily, who was born in VT, living in Grand Traverse County on the 1870 census.
I then checked in 1860 to try to find this family to see if they had a child Warren.They did.
1860 US census, Andover, Ashtabula County, Ohio
Fisher, James, 44, NY
Emily, 40, VT
Lenora, 19, NY
Warren, 13, NY <---
Cornelia, 9, PA
Willie, 6, PA
John, 5, PA
Katy, 1, OH
Then back to 1850, where another clue that this is the right family.
1850 US Census, Girard, Erie County, PA
Fisher, James, 36, laborer, NY
Emily, 3?, VT
Harriet L, 11, NY
Mary E, 8, PA
Warren L, 3, PA
Note:change in Warren's birth location, the later listing might be just poor memory of his parents, or this one could be.
Anyhow, I'm pretty sure this is the right family.
It would pay to check for probate on James and Emily Fisher if you could find them to see if either listed your Warren as their dependant.Also their might be obits for some of Warren's siblings that would verify this for you.
Marriage Record from Grand Traverse County.
ALMIRA - POTTER,WARREN L FISHER,GR TRAVERSE,--,,30 APR 1868,--,--,--
I'm not related.