Marriage date and place from “Scotland, Marriages, 1561-1910” on familysearch.org.

There is a widowed John Forest, age 84 (so born around 1787), living with a Janet Forest, age 59 (so born around 1812), living together in the 1871 census for McNab township in Renfrew, Ontario. They are both listed as being born in Scotland. This may be the same John, and an umarried daughter).