I want my mom to look at me as and adult not a child.my bothers acting crazy. what would you do?

guys it seems like im in a standstill I have two degrees and live with my parents.Im a boomerang kid that means after I graduated from college I came back home that was the worst thing I couldve did. Im my mother biological baby girl, so thats how my mom looks at me...as the baby... the same day I graduated from college was the same day she adopted kids and they came to live with us(that means no time for myself) I love the kids but they kindve take up my time.... besides I talk to my friends who graduated also and married, have kids... have their own lives... living out of town... but Im the one whose mom still tells her what to do..and also Im like a mother to the kids.besides them, my mom adopted a boy my freshman year of college. when I grad and came back home, the boy is acting crazy... hes smoking, lying, he steal from me every chance he get, we gotta lock our door when we leave the house, calls me b***h but she doesnt hound him half as she hound me and im 25 years old he15