Ajay
In the book Ajay wishes he was more like his brother. As the book progresses and his brother becomes brain damaged. Ajay grows into a big brother figure in his own eyes. he also fulfills his brother's dream and gets good grades at school.
Birju's brain damage
Birju's brain damage paints an image in the narrative of how the main reason they moved was a shallow reason. The father in the story had such great faith in western medicine, and as his son is in hospital nothing is able to save him. This is too much for the father and he falls into alcoholism.
Brotherly Relationship
This image is built and destroyed and then rebuilt in the book. It shows as we see the two brothers dynamic, but then it gets destroyed when one brother has his accident. It has then need to rebuilt in a new fashion as Ajay has to discover his place again.
Faith
The faith in the relatives' God grows as they are hit with real life. Their faith was dead and in its replacement was wester medicine. Ajay, prays more and more often after his brother accident and he is the one that copes with the accident best, maybe because of his faith.