So I know what the curse is, and I know that he didn't know it, because if he had he would have bitten the bullet and brought her mother and her back to Goldengrove, knowing she would be his only child, instead of taking her birth as proof he was having bad luck with barren wives.
The thing is, I don't know who laid it. And once Anastasia learns of it, she cares a great deal. If she could preclude its being directed at his house, rather than him, she could live with it easily, but only if she knows who can she know that the angry source won't come after her.
The problem is that while the world has a profusion of people who have mildly good reasons to curse him, none of them have powerfully strong ones, or ones that resonate strongly with the themes of the story.
Ah, well, that's the art of writing. Figuring out something like that and marrying so well with the rest of the story that even you can't figure out where the original stuff was and where you had to add.