I am surprised that Isabella’s racist assertion that Heathcliff looks like the local fortune-teller’s son
(“The cowardly children crept nearer also, Isabella lisping “Frightful thing! Put him in the cellar, papa. He’s exactly like the son of the fortune-teller that stole my tame pheasant. Isn’t he, Edgar?”)
is taken here as a hint that Heathcliff really is the local fortune-teller’s son.
You would think that this is not Wuthering Heights but Kate Chopin’s “Desiree’s Baby”.
I find this to be an interesting reading and would be open to a fanfic with this premise, but I think the line’s intention is more “garden-variety racism” than “secret parentage conspiracy”.
There really are readings as varied as there are readers, especially with this book.
Edit:
In “Desiree’s Baby” too:
“The baby, half naked, lay asleep upon her own great mahogany bed, that was like a sumptuous throne, with its satin-lined half-canopy. One of La Blanche’s little quadroon boys—half naked too— stood fanning the child slowly with a fan of peacock feathers. Désirée’s eyes had been fixed absently and sadly upon the baby, while she was striving to penetrate the threatening mist that she felt closing about her. She looked from her child to the boy who stood beside him, and back again; over and over. “Ah!” It was a cry that she could not help; which she was not conscious of having uttered.” (italics mine)
We first think that this line is about Desiree’s baby being a quarter Black like “La Blanche’s little quadroon boy”, and indeed that’s the case. But I think if we closely read the short story we can also theorize that Desiree’s baby and La Blanche’s son are siblings, I think it is implied that Desiree’s husband is sleeping with his slave La Blanche:
“And the way he cries,” went on Désirée, “is deafening. Armand heard him the other day as far away as La Blanche’s cabin.” (italics mine)
Why is Desiree’s husband at La Blanche’s cabin? I think he is the father of her child.
This theory that Heathcliff looks like “the fortune-teller’s son” because they are siblings and not just because they are of the same ethnicity reminded me of this line and this implication in this short story.
I wrote my undergraduate thesis about “Desiree’s Baby” and I think the fans of discussing Heathcliff and the “Heathcliff Earnshaw” theory should read more American fiction on race. They play with these ideas even more than Wuthering Heights.