How did Estha and Rahel evolve throughout the story ?

This is such a detailed question for this short-answer space. The twins move closer and closer to each other as their world becomes more chaotic. They are increasingly extranged from the world with the disintegration of their mother Ammu. By the end of the novel they meet after a long absense from each other. They actually have a sexual encounter which is Arundhati Roy's way of making the Twins one person.