Perhaps I misunderstood. Or perhaps I'm just backward in my thinking. But I see very little romance, or much of anything good, in the relationship between Christine and Erik. He is scarily possessive of her, not to mention extremely violent. Maybe I'm in the minority, but I don't find the desire to own another human being to be even a little bit romantic.

The Valjean/Cosette relationship and your suggestion that he falls in love with her doesn't seem incestual so much as overprotectively dadlike. Unless you are making insinuations toward an outright sexual relationship between them, which would be a little icky if only because they've lived as father and daughter for ten years.