Hello.

I am 23 years old. I live alone. A little while back, I got into some trouble, and lives with my older sister, and her boyfriend.
(To male this story clear, I must explain this : my dad got With my mom, who is my older sisters mom. They had me. He is not my sisters dad. A few years later, he gpr with my sister, and had my half little brother)

Well, my dad is dead now, and I have moves on. But when I stayed with my older sister for a few weeks... her house was disgusting, she always made my little brother do all.the chores, and made him watch her two kids which she had with her boyfriend. My brother has told.me that the boyfriend has beaten him, and always mentally abuses him. He is a skinny kid. This Guy is huge.(the boyfriend)
I also discovered that they were selling drugs, and growing pot in the closet. I have already called CPS once, but I do not know what else I should do. I want to take care of him. Can anyone please help?

You need to follow up with CPS. Tell them you are willing to care for your brother. But unless you can show a stable home environment with the ability to care for him, then may place him with someone else.