I've been praying for a cousin of mine who lives with my family to leave this house or change. His mother has left with his sister to another state but he stayed behind. He uses drugs and steals from us. He causes my family and I anxiety and stress. I can't sleep thinking he will try to pick the doors open to get money or other expensive items. He won't live with his mother and my mom won't kick him out. I have prayed to the Lord Jesus. But I am really running out of patience, and I can't live like this nor my family.
In families who are dealing with a drug addict, there is almost always an enabler present. The enabler is the person who mistakenly thinks that the addict can be rescued by protecting him from the consequences of his actions. Wrongs that are done are overlooked in the name of "peace." The addict is shielded from the consequences of his actions because, after all, he is family. Meanwhile the addict is convinced that using drugs isn't so bad because almost nothing bad happens to him. There is no reason to change because he is satisfied with the way things are.
Your mother is the enabler. She mistakenly thinks she can rescue your cousin through kindness and nothing will convince her otherwise. But the reality that you have to face is that you don't run this household. You don't own the house. You don't pay the bills. You can express your thoughts on matters, but in the end it is your parents' decision. About the only thing you can do is choose not to live in the house if you are old enough to leave.
I know it is not what you want to hear, and I can't offer a "magic" solution to these problems.