Epigraphs are like little appetizers to the great entrée of a story. They illuminate important aspects of the story, and they get us headed in the right direction.
"These casual exfoliations are/Of the tropic of resemblances..."
It's not a surprise that García grabs these lines from Wallace Stevens ("Someone Puts a Pineapple Together"), since she kept copies of Stevens' poetry on her desk while she wrote Dreaming in Cuban. These particular lines are a meditation on metaphor. In this poem, Stevens lists twelve different ways of perceiving and "creating" a pineapple through language, and includes things like "The hut stands by itself beneath the palms" and "The Owl sits humped. It has a hundred eyes."
If you spend any time in a literature classroom, you'll hear your teacher or professor talk about "exfoliating" a poem or literary work, as though it's skin is aging and you need to take it to spa for cleaning. But cut your teacher some slack, because the comparison is relevant. To exfoliate something, you have to peel back the layers of meaning (the "resemblances") to get at the heart of the idea—to know something for what it truly is.
So perhaps by exploring how each member of this family interprets the events of their lives, we might piece together a picture of what their life together has really meant, and where it might be going.