Under Canadian law, there is no fixed age at which a child is legally entitled to choose which parent he or she prefers to live with, after they separate and divorce. If a custody dispute arises and the court is asked to make a ruling on this point, the court will always do so after taking the best interests of the child into account, regardless of the child’s age.
With that said, one of the many factors that a court must look at to make that “best interests” determination, is the age of the child, and whether he or she expresses a stated preference to live with one parent or the other. For example — and provided those best interests are still safeguarded — a court may defer to an older teenager’s stated choice when making its custody ruling. This is even more likely if there are practical considerations at play, e.g. the court is unlikely to make a ruling that is contrary to the teen’s steadfast wishes, if it will be challenging for the parents to enforce the ruling by making the teen live where he or she does not want to.