" I look at the teen vogue article again, studying the facts about the Donor Sibling Registry and how it matches up donor offspring with their sisters and brothers, if possible. I realize now how big the if really is (53)."
This quote is from when Tate gave her the article in a magazine that said you could go to a site and type in information about your donor and it will tell you whether that donor had anybody else. I think she starts to think there isn't a chance and that there is a really big if because she is afraid of what she will find out. She doesn't know if she needs anything to complicate her life anymore.
A theme that I see emerging in this book is about finding yourself and figuring out who you are. Since the beginning on the book Jenny is trying to figure out what she is good at and what she likes to do. She knows she doesn't fit in with her family because they all love sports and are great athletes, she isn't. She is trying to figure out where she fits in and she talks about how she doesn't think she fits in anywhere and can't even like this boy Tate. She is always down on herself and i think throughout the book she will keep trying to figure these problems out.