My Mate is My Step-Brother

AUTHORS NOTE:

This is undergoing major editing. I started writing this when I was young, so please just accept what I've done and don't comment on how something is bad. Be constructive in criticism.
I really enjoy the concept I've written, and I believe it to be unique. It has been known to cause some confusion so always message me for more information or clarity. All I ask is that you take time to read the entire thing before you make a judgment. Thank you and enjoy the story!

Cassandra hasn't known feeling since 15. She is full of hatred and betrayal. She doesn't feel happiness. She doesn't know love. Until he came along. Just the sight of him made her feel. However, there is a slight problem, he's her step-brother.
19 year old, Alex Levon, is alpha of the Night Bound pack. He was chosen because he was ruthless and cold-hearted. Then, one day, a beautiful girl comes to the pack. This girl's father was the Alpha before himself. His wife was his own mother. His wolf tells him mate. There is a slight problem, she was already mated, sort of, and he's her step-brother.
Hunter was a player. He left for three years and then came back. He always got what he wanted and women practically threw themselves at him. However, on the first day back, he sees the most beautiful girl in the world. His wolf tells him mate. Oh and did I mention that they're they're step-siblings?

However, more is in store for Cassandra. More than the two mates she thought she would need to choose from. Things she deemed impossible. And when the time comes, will three people be able to join forces against the greatest of evil? Even after all the pain?