Take your little brother out rowing late at night in a very deep lake and tell him a story about how a mermaid in the lake grants wishes if you stand up in the boat and lean over to kiss the water. Your brother's wish won't come true, but if you row fast enough, yours will.

In all seriousness though, this is a tough row to hoe. I have a special needs step-sister and she will never be okay. Luckily, my mother and step-father take care of her now, but if one (or both - God forbid) were to pass, then I'd likely have to take on responsibility. That's a reality in my life and your brother is a reality in your life.

You absolutely need to make space for yourself and you absolutely need to take care of your family. The answer isn't any one thing. It will be a lot of balancing and work. Will they be okay if you move out? If not, how can you make that okay? Will you be okay if you don't move out? Will your relationship be okay? It's not simple and we don't have all the details. Basically, you just have to understand that this isn't a choice of one or the other but about working hard enough to figure out how to take care of both your needs and those of your family.