Hi!
Self-soothing is a skill we can all use and probably most of us need some help with it. Listening to music works for me, but I have to be careful of what type of music it is. It has to be something fun or at least emotionally neutral to me. If I listen to something that matches my mood or the mood I am heading towards? It is not good.
LT mentioned meditation and that is also a good thing. I have a hard time with the more traditional meditation techniques. I can't clear my mind and I tend to fall asleep.

What I used to do when I could was walking meditation. Now I do mindfulness. Not with emotions, though that is important too, but with whatever task I am doing whether it is wahing dishes or even in the shower. I focus on the feel of the water, the smell of the soap how the lather feels on my hands, the feel of the dishes etc. It helps me to focus and n that sense it clears my mind.
We also have a thread on distress tolerance skills that are taught in DBT which are great for anyone to learn. Check out this thread here:
https://bpdfamily.com/message_board/index.php?topic=331665.0 and see what you think.
another thing that helps me is to check my thoughts and expectations. If you have repeatedly asked your brother to help and he refuses he is telling you through his actions what he is willing to do. Yep, it is not fair. Is it helpful to you to keep asking him though? Or to keep getting angry that he is being who he is? I am not saying to be happy about it. I am saying you can't change it and chances are the more you ask the more he is going to dig in. Radical Acceptance can help with this.
What do you think?