Should I be amended at 15?

My mom and step dad got married and had two children of there own. My sisters 8 and my brothers 6. They buy them better clothes and treat me totally different (like a thirt wheel). We live in my grandparents home so I would not e all on my own. I am the only person who cleans cooks and watces the 2 kids. My friends mon rem said she woils adopt me if I need help. I just need some real advice b4 I leave and regret it. Plz help me!