Kim Potter and the Mystery of who she is

This is my 1st Harry Potter story. Please tell me what you think. Kim is James's cousin but she is related to him in another way too. The story will flashback to how this began.

Chapter One- Waking Up Wet

On the morning of September 1st, a teenage girl was woken up by her cousin and his best friend by them spraying her with water from their wands. She sat up in her bed soaking wet and started to yell,

"James Harold Potter and Sirius Orion Black, what in the name of Merlin did you think that you could wake me up with water!"

James replied "You weren't awake yet and you need to get dressed and eat your breakfast before you catch the train."

Sirius chimed in "You don't want to be late now do you, Miss Head of Houses."

"James, Sirius, Kim, Time for Breakfast", drifted up the stairs from the kitchen.

Kim jumped out of bed, pushed the boys out of the room and closed the door. She quickly got changed into her school uniform and pinned her badge to the front of her robes, grabbed her wand, ran out of her bedroom, down the stairs to the kitchen. James and Sirius were shoving food down their throats when she walked in.

Kim sat down and said "Good Morning Aunt Helene and Uncle Harold", to her Aunt and Uncle sitting down the end of the table.

"Good Morning Kim, are you ready to go back to school" asked Aunt Helen?

"Yes", replied Kim while starting to cut up the pancakes on her plate.

"Try and keep these two out of trouble this year", said Uncle Harold.

The boys let out a string of curses.

"I'll try" answered Kim.