Yes, but you can get married as a minor with parental consent. In Canada I understand your minor age limit is rather low? If homosexual marriage is legal what is to keep what right now is being seen as statutory rape from being reclassified as "romance"? And if the parents object to the relationship what will they be considered? Protective or bigoted?
You also just made a really good point however. If they are underage it is classified as "rape or sexual assault, not homosexuality" yet it happens all the time. Why is it not classified as homosexual behavior? That is what it is, just as statutory rape by someone of the opposite gender is heterosexaul behavior.
These are real people out there who are seeing this as the first step to attaining their goals. They have even gotten some psychologists on their side who have done studies on adult/child sexual relationships where they have concluded that such relationships are "natural", "normal", and "healthy" based entirely on what the participants "feel".