It could happen, and perish the thought. Sparkles could only be the "Queen Consort" as the wife of a blood heir (harry), but you can bet she would be the power behind the facade. Harry is next in line to take the throne if something were to befall Charles, William and all William's children at once, like an earthquake or drone strike when they were all together. And I wouldn't put it past some of their "friends." Obviously harry has no clue that he is just being used, and not only by her.
It would take an act of Parliament to put harry out of the line of succession—the Queen can't just decree it in a Constitutional Monarchy.
Um, nope.
Queen consort:
A queen consort is the wife of a reigning king, or an empress consort in the case of an emperor. A queen consort usually shares her spouse's social rank and status. She holds the feminine equivalent of the king's monarchical titles, but historically, she does not share the regnant’s political and military powers.