In divorce proceedings between the parents of a child, leave to apply for custody under section 16(3) of the Divorce Act may be granted to non-parents whose claim is not frivolous or vexatious. The onus of proving that the claim is frivolous or vexatious falls on the party opposing the application. Maternal grandparents with whom the child had been living may be added as third parties to a divorce proceeding between the child’s parents, both of whom were opposed to the leave application.351
 Boychuk v Boychuk,  AJ No 1578 (QB). See Chapter 12, Section E(6).