My mom had me at fifteen...?

wow. your baby brothers are not your responsibility. you need to tell your mom you refuse to look after them. if you can tell your grandparents about what she is making you do and ask if can live with them so that you can go to school like a normal kid. if not, call child and family services. it may sound harsh but those aren't your kids. why should you have to give up your childhood just because of your mom.