More fairy tales.
But -- Did the heroine meet up with the right prince? What if I switched him? Wouldn't the cousin (to be born in the current story, as the first prince is) actually be a better target for the witch, because he's the grandson of the witch who wronged her, not the son of her stepdaughter? Or could she go after him a different way than she's going after his cousin and the heroine?
If the cousin has his story after -- and I already have ideas about the princess he will go to rescue -- does it start while these two are getting together or surviving being together? That would add cliff-hanger-y elements to the story.
And what else is going on? In the current story they are told that not all spells break just because the witch who cast them died. And the cousin is going to have the same power as his mother does in the current story -- to see through things that hide a curse and so prevent your breaking it. What curses are lingering for him?
Meanwhile, the prince's sister will marry and there will be a lot of jokes about how her escort must prevent the whole "goose girl" thing.