Quote 82
Nenny and I don't look like sisters…not right away. Not the way you can tell with Rachel and Lucy who have the same fat popsicle lips like everybody else in their family. But me and Nenny, we are more alike than you would know. Our laughter for example. (7.1)
Esperanza seems to recognize that certain similarities are more important than physical ones. She seems to consider the fact that she and Nenny have the same laughter to be a stronger bond than if they looked alike.
Quote 83
Look at that house, I said, it looks like Mexico.
Rachel and Lucy look at me like I'm crazy, but before they can let out a laugh, Nenny says: Yes, that's Mexico all right. That's what I was thinking exactly. (7.4)
It means a lot to Esperanza that her little sister understands her perspective. Even though she's too young for Esperanza to consider her a friend, Nenny understands what Esperanza is trying to convey in a way that her friends do not.
Quote 84
If you don't get them you may turn into a man. Nenny says this and she believes it. She is this way because of her age.
That's right, I add before Lucy or Rachel can make fun of her. She is stupid alright, but she is my sister. (20.5)
This is classic older sibling syndrome – Esperanza picks on her little sister all the time, but she won't let anyone else make fun of Nenny.