In
Great Expectations I have always assumed that Estella was a few years older than Pip, but I can't seem to find explicit confirmation of that. Anyone know for sure?
If I'm right, then the relationship between Pip and Estella is pretty toxic for most of the book - and
this article says the original ending wasn't a happy(ish) one, and others convinced Dickens to change it.
... Just seemed like the sort of literary thing that might fit with the OP requirements.