Elle and Flynn were born at the same time and moms were best friends, so they were raised like twins. but they came up with special rules when they were 9 that they must follow, including dating siblings is totally off limits. But Elle has a secret crush on Flynn's brother Noah.
Elle and Noah end up kissing each other at the school fair when Flynn went off with the girl he just met. She tells Flynn and he is mad but tells her not to do it again. Elle gets a ride home from Noah and they end up kissing each other again and Elle is not sure how to tell Flynn and whether they should date each other.
Noah takes Elle to the Hollywood sign where they both make up 3 rules together about their relationship, including that no one can know until Elle can find a way to tell Flynn.
Elle and Noah start dating but are finding it challenging keeping it secret from everyone. Flynn doesn't get suspicious yet because he is dating another girl but starts to feel that something is wrong because they don't hang out as much. Elle also finds out that Noah will be leaving for College next year for Harvard.
Flynn finds out that Elle and Noah were dating and sleeping with eachother and is angry and stops talking to Elle. They don't talk to eachother for a couple of weeks and Elle and Noah broke up and he stopped coming to school. Elle tries to make it up to Flynn but he is too mad. He made up that rule not to date siblings because he was sad that hi brother had everything he ever wanted except Elle.
After weeks of not talking to eachother Elle and Flynn become friends again when they do Their favourite thing dancing. They have their 16th birthday part but Elle is sad that she isn't with Noah and tells Flynn who helps her find him because he left for College. She finds Noah and they start dating eachother again but he leaves for college.