Day of the butterfly what is the author's main purpose for including this description of myra and her brother.

The author's main purpose for including the description of Myra and her brother is to show that Myra how being responsible for her brother impacts on her ability to have friends. Instead of playing on the field at recess, she sits in the neutral zone with her brother. As a result,  she is teased by the girls in her class. After a while, Myra becomes sick and ends up in the hospital. After that, all the girls in her class suddenly care about her and visit her.