THE CHARLOTTETOWN GUARDIAN, WEDNESDAY, JANUARY 24, 1906
DEATH: STEWART-MACINNIS - At Head St. Peter's Bay, P.E.I., on Jany. 13th inst., Mary Stewart, wife of the late Martin McInnis, Esq., in her seventy-ninth year.
Here is Mary Stewart's death announcement There are records of another Martin McInnis in some of the census who lived in Lot 55 he was a merchant and a ship builder. It looks like he was married to Mary Stewart until the time of his death.
I did a little more research on Martin McInnis of lot 59(Commercial Cross) and found some records for his children on familysearch. He's also listed in the Meacham's atlas as living in lot 59 in 1880.
Here is Margaret McInnis's death record and it states her mother was an Annie Matheson so she was probably Martins first wife.
Name: Margaret Mcinnis
Event Type: Death
Event Date: 04 Jan 1903
Event Place: Waltham, Massachusetts
Residence Place: Watertown, Massachusetts
Gender: Female
Age: 30
Marital Status: Married
Birthplace: P. E. Island
Birth Year (Estimated): 1873
Burial Place: Watertown
Father's Name: Martin Mcinnis
Father's Birthplace: P. E. Island
Mother's Name: Annie Matheson
Mother's Birthplace: P. E. Island
Spouse's Name: Stanley Mcdonald
Martin McInnis (the son) marriage records to Margaret Nicholson state his father as Martin McInnis and mother as Catherine MacDonald so she would be the second wife of Angus and mother of the younger children. Annie Matheson must have died sometime in the late 1870's and then he married the much younger Catherine.
To confuse matters more he had three children with another Catherine or Kate whom he never married.
