Fury shall reign (A Game of Thrones fanfic)

I Do Not own game of thrones or anything except the people I create and my storyline.All rights to the amazing George R. R. Martin.So I'm planning on doing a GoT fanfic because I love the show and the books.I'm still working on things.Also things will be changed to suit my story.But now let talk about my OCs.This is my first story so tell me your honest opinion
Cersi and Robert had a trueborn twins.
Their names are Aleksander and Joanna Baratheon.I am Aleksander of House Baratheon, First of his name, King of the Andals, the Rhoynar and the First Men, Lord of the Seven Kingdoms, Protector of the Realm. Others may claim themselves as Kings but I am the true King of this realm, let all pretenders fall before my sword. I am Joanna of House Baratheon. My brother is true king, I must help him win The Clash of Three Crowns by any means necessary.

Rating could change
PG-13 for language