The Mystery of Annie May Buchanan 1884-1890

My cousin Barry had directed my attention to the records for Trinity Anglican Cemetery near Donegal, Perth, Ontario. This was a pioneer cemetery where some of my Buchanan family were buried. One grave in particular has puzzled me for a long time.

Annie May Buchanan
BIRTH 1884
Perth County, Ontario, Canada
DEATH 18 Jul 1890 (aged 5–6)
Elma, Perth County, Ontario, Canada
BURIAL
Trinity Anglican Cemetery
Donegal, Perth County, Ontario, Canada
MEMORIAL ID 154530855 ·
https://www.findagrave.com/memorial/154530855/annie-may-buchanan

She is not mentioned in the Buchanan Family Tree book or any other family records. Her life fell between censuses, so she is not mentioned in the Canada census. Her birth is not recorded in the government records. (There is an Annie May Buchanan born 29 May 1888 in the area, but we know who she is, and she married Norman Acheson and died at age 70, not as a young child.) So who is the mystery child?

This record adds some information.
This is record 013889, located on page 511 of Schedule C - DEATHS
Anna May Buchanan
died July 18th, 1890
Female
6 years
Farmer's daughter
born Elma [township, Perth County]
Diptheria
duration 11 Days
physician Dr. Hamilton
informant Charles Buchanan
Gentleman, Elma
registered August 27th, 1890
Church of England
registrar Thos Fullarton

The informant for a death is normally a parent, spouse or adult child. Charles Buchanan was my great grandfather's brother. In the 1891 census he also gives his occupation as "Gentleman", so he is the right person. But there is a complication. Anna May was born about 15 years after Charles's youngest known child, so he is almost certainly not the father. He is probably the grandfather. He had five sons: Andrew, Thomas, William, John, Charles. Unfortunately I have no record of any of them being the father of Annie May, but one of them almost certainly has to be. Let's look at the possibilities:

Andrew born 10 Nov 1848 and died the following year. So it can't be him.

Thomas, born 15 Mar 1851, and married Ellen Cochrane 24 Dec 1875, and his family moved to Manitoba in 1881, so he would not have a daughter who died in Ontario in 1890.

William, born 8 May 1856 and married Mary McGregor 19 Apr 1882. At the time of the 1891 Canada census they were living in Grey County.

John, born about 1858 became a good prospect, so I spent considerable time researching him. The family records have almost no information other than saying that he had a wife named Mary and a son named Charles Henry, and was living in Michigan at the time of his father's death. He is found in the 1861 and 1871 Canada censuses then disappears. His sister Jane's obit says he is living at  Whittmore, Michigan, USA. Google maps identifies this as Whittemore, in Burleigh township,  Michigan. I then found him in the 1894 Michigan censuses and the US censuses for 1900, 1910 and 1920. Except his wife's name is given as Belle. Then I found a marriage record. 

Michigan Marriages, 1868-1925

Name: John Buchannan

Event Type: Marriage

Event Date: 28 Apr 1882

Event Place: Bingham, Huron, Michigan

Age: 21y

Birth Date: 1861

Birthplace: Ontario

Spouse's Name: Isabella Mary Campbell

Spouse's Age: 25y

Spouse's Birth Date: 1857

Spouse's Birthplace: Ontario

[This in turn led me to her parents and siblings.]

If John was living in Michigan in 1882, he would not have a daughter living in Ontario in 1884-1890. 

Charles, born May 1865, would have been 19 when Annie May was born, so he is probably not her father. In the 1891 census, Charles is single and living with his sister's family. On 6 Dec 1916 he married Janet Elizabeth Anderson. 

The best possibility seems to be William. We do not know when he moved to Grey County.

Charles is a possibility, but William seems the most likely father of Anna May Buchanan 1884-1990.