If you touch my sister, ill kill you

In august 20 of the year 1992, the twins Demi and Dani were born. Demi is a rebel girl who cares most about her bands than school, she likes to change her hair color every then and has a couple of tattoos. She is the most extrovert girl in school and has a lot o friends. But even though she is like that, she has one big sweet and kind heart. She loves her family and will hurt anyone who mess with them, especially with her sister, Dani, she will be a great support for her during her tough times. Dani is like the most sweet girl that you can imagine, she is so kind and has a lot of respect for everything and everyone. She is kinda the opposite of Demi, she is very shy and introvert, and as you may imagine, she doesn't have as much friends as her sister does. She doesn't like the tattoos and hair changing of her sister. You'll find along the way of this story that a inherited disease is not so fun. What kind of disease is this? Well you'll find out later on. But for now you can now that this will make Dani a little vulnerable and Her family overprotective. ---------------------------------------------Sooo i have this story in mind but i have no idea how a story is written so this might be confusing for you, and english is not my mother languaje soo. This might just be like a oneshot or a short story.