One of the most contentious issues around child support is defining what a child of the marriage is. The Divorce Act states:
(2) CHILD OF THE MARRIAGE — For the purposes of the definition “child of the marriage” in subsection (1), a child of two spouses or former spouses includes
(a) any child for whom they both stand in the place of parents; and
(b) any child of whom one is the parent and for whom the other stands in the place of a parent.
This definition means that children do not have to be biological if the in loco parentis test is met. It also means that children who have continued their education into their 20s can still be considered children of the marriage.
These definitions can also vary across jurisdictions in Canada. In Ontario, s. 1 of the Age of Majority and Accountability Act states “Every person attains the age of majority and ceases to be a minor on attaining the age of eighteen years,” whereas s. 1(1)(a) of British Columbia’s Age of Majority Act says “a person reaches the age of majority on becoming age 19.”
The leading case for step-parents is the Supreme Court of Canada case in Chartier v. Chartier, where the court looked at the actions and intentions of parents, and stated:
38 …The appellant argued that the test for whether or not a person stands in the place of a parent should be determined exclusively from the perspective of the child. I cannot accept this test. In many cases, a child will be very young and it will be difficult to determine whether that child considers the person as a parental figure. Further, an older child may resent his or her step-parent and reject the authority of that person as a parent, even though, objectively, that person effectively provides for the child and stands in the place of a parent. The opinion of the child regarding the relationship with the step-parent is important, but it constitutes only one of many factors to be considered. In particular, attention must be given to the representations of the step-parent, independently of the child’s response.
The definition of in loco parentis has been applied quite broadly by courts. In Gardiner v. Gardiner the Supreme Court of Nova Scotia held that a woman who had no intention of adopting children but treated them kindly while living in the same house as their father stood in the place of a parent.

