Though Rahel and Estha are both the protagonists of this novel, we get to know Rahel more completely, since we spend significantly more time seeing the world through her eyes. As a child, Rahel exists in a kind of harmony with Estha, her twin brother who is eighteen minutes her senior. Their personalities seem to balance each other out, like popcorn and M&Ms or peanut butter and jelly. Estha is serious and earnest; Rahel becomes preoccupied with things and can't seem to sit still. Estha seems to be the better behaved of the two; Rahel is the one who hides in the dirty airport curtains when she doesn't want to say hi to Sophie Mol.
Rahel also has an incredibly active imagination – she seems to exist in a version of reality that's all her own. When she feels scared, she feels Pappachi's moth crawling on her heart with icy legs. At Sophie Mol's funeral, she thinks she sees her turn over in her coffin, which further convinces her that Sophie Mol is being buried alive. She sees the kangaroo-shaped trash receptacles at the airport rummaging through their pouches for cigarettes and cashews.
Rahel's imagination is very different from Estha's – hers is more childlike and wondering, while Estha's is more like a worst-case-scenario handbook. The ways they think about and respond to the world around them reveal a lot about the separate paths their experiences will take. Even though Rahel finds things to worry about that are pretty serious, like whether Ammu has stopped loving her as much as she used to, we know things are actually OK for her. She's safe, and she's loved. Any of us would be insecure about Ammu's love if we were in her shoes, but in comparison with Estha's anxiety about being molested again, it's safe to say Estha has more pressing concerns.
In fact, one of the really interesting ways the narrator shows us the difference between the twins is by looking at the way they understand Velutha's death. After Estha is coerced into telling the inspector that Velutha kidnapped him, he tells Rahel that everything's OK – it wasn't Velutha; it was his long-lost twin. Even though we don't know if Rahel totally buys it or not, we see that she finds a safe space to hide in her imagination, while Estha has to deal with the truth.
We learn that after the family is split up, Rahel is sent away to school. She is expelled for misbehavior though her personal brand of misbehaving is kind of harmless and weird: decorating heaps of dung (poop) with flowers. The last straw at one school comes when she hides behind doors and pops out to collide with unsuspecting senior girls. She gets thrown out of two more schools, one for smoking and one for setting someone's hairpiece on fire. In every case, the narrator tells us, Rahel's teachers note that she is an extremely polite child who has no friends (1.102). When we think of how she's been separated from Estha, her other half, we can see how Rahel would be kind of a lost soul.
Rahel continues to wander until she returns to Ayemenem at the age of 31. She enters an architecture program in Delhi, not because she's particularly interested in architecture, but more because she just falls into it. The same seems to go for her marriage. We find out that she meets Larry McCaslin, who is doing research in Delhi, and goes back to the United States with him. We don't really get the vibe that she's that into him – and neither does Larry, really. Whenever they make love, he feels like she's not paying attention. The narrator doesn't give us too many specifics about the end of their marriage, which is fitting when you think about how Rahel spends most of her adult life drifting from one thing to the next. She works various jobs all over the U.S. before returning to Ayemenem.
We learn that Estha is really the only reason she returns. Even though she hasn't seen him in 23 years, we can sense that he's still the most important person in her life. Whenever they are close, they don't even have to speak to know the other is there. (Not that Estha would speak anyway these days.) They still have an innate sense of being completed by each other. This sort of helps explain why Rahel and Estha have sex at the end of the book, although the idea of incest is really uncomfortable for most readers. Being together makes the two halves a complete whole.