The Supreme Court of Canada endorsed what is known as the “mature minor” doctrine in 2009, which means that a child of any age can give consent if they have the maturity and capacity to make informed decisions and understand the consequences of said decisions.
Some provinces have legislated what age an assumption of maturity occurs at. In Quebec it’s 14, Manitoba and the Maritime provinces 16. But in any province a child of any age may petition the court. Of course this usually happens when the parents are divorced.