Thank you for your letter. I hope I can offer something useful.
Fifteen is a rough age because you are in-between everything, and are just starting to see weak spots in your family and the world. It is very normal for teenagers and their parents to go at it during this time, and for the siblings to throw in with the mix as well. But I understand the fact that it is common doesn’t offer much comfort.
Probably the best-known book about teenage girls is Reviving Ophelia: Saving the Selves of Adolescent Girls written by Mary Pipher. I’d recommend reading it—see if you agree with the author, then ask your parents to read it. Sometimes an outside source can help make the change.
But my guess is that you are going to need a few sessions of family therapy. The fact that you are hurting yourself because of all this demands something is done sooner rather than later. I would ask your parents directly to have you talk to a therapist, and then explains to the therapist what is happening. More than likely the therapist will engage at least one of your parents, if not the whole family.
Don’t suffer in silence with this. If your parents are not willing to take you to a therapist, talk to the school counselor or a trusted teacher. He or she will be able to help get the ball rolling.
This may be a tough time for you, but there are many good things waiting for you as you move through high school. As you are seeking some peace within the family, keep developing interests outside of the home: Clubs, sports, classes, etc. Work on developing yourself, not focused any on the family feud.