Sk8R,
good question,
In Ontario this what is says in the Family Law Act spouse is defined see link below.
http://www.e-laws.gov.on.ca/DBLaws/S...0f03_e.htm#BK0
Definitions
1. (1) In this Act,
“spouse” means either of two persons who,
(a) are married to each other, or
(b) have together entered into a marriage that is voidable or void, in good faith on the part of a person relying on this clause to assert any right. (“conjoint”) R.S.O. 1990, c. F.3, s. 1 (1); 1997, c. 20, s. 1; 1999, c. 6, s. 25 (1); 2005, c. 5, s. 27 (1, 2).
In regards to support obligations
PART III
spouse is somewhat defined further (for support purposes)
Definitions
29. In this Part,
“spouse” means a spouse as defined in subsection 1 (1), and in addition includes either of two persons who are not married to each other and have cohabited,
(a) continuously for a period of not less than three years, or
(b) in a relationship of some permanence, if they are the natural or adoptive parents of a child. (“conjoint”) R.S.O. 1990, c. F.3, s. 29; 1999, c. 6, s. 25 (2); 2005, c. 5, s. 27 (4-6).