My first YA book

So I completed the profile of main character in the first book of a YA series I plan to write. I've also completed the first chapter. I like it. I've sent it off to my 17 year old sister, who I am using as a sounding board and collaborator for this book. This new series is about the descendants of Elemental Aliens who had to flee from their home planet due to it's impending death, and had to resume their lives on Earth. Each book will be about the last descendant of the five elemental aliens that came to our planet, Air, Earth, Water, Fire and Metal. They will deal with their own personal troubles, a long with finding out who they truly are and how they are all connected to each other. I hope that this will be a successful series.