You are not a murderer. It was a complete accident. I completely understand your grief. But think of your parents and what it would do to both of them if you weren't there. They understand it was a mistake and they might be feeling they same as you are, because they weren't there for both you and your brother. I think maybe talking to them, tell them how you feel. Therapy is great but talking to your loved ones could help more.

And what if you lived your life for your brother? Let him be your purpose, your drive to do the best you could do in life. See the world, create something that saves lives , create a business that helps others that are in your situation, dedicate everything you do to your brother, find a loving woman name your son after your brother. You seem like a person that doesn't just want to forget about this, So dont forget about it, find the ways to move past your grief and live your life for him, and your parents. (As a father of two sons, I would be a complete zombie for the rest of my life if I lost my last living son to suicide. ) not only because of the suicide, but also because I would feel like its completely my fault, because I either didn't know how to help you, or that I was too blind to see that you needed help. And I am almost positive it would tear my wife and I apart as well. You are the glue holding everything together. You are very important to everyone around you.

Suicide is not the answer. Find your path.
Grow from this, experience live because of this, love yourself and others more, and enjoy your life and the lives you create for your brother. When it's truly your time, with a great wife and kids and many more grand kids standing by your side, you can then finally meet back up with your brother.

I'm sorry I'm not good at this stuff. I just felt like I had to write something here, Because I'm a father. I had no clue how important my life was until I had children.
I understand your sorrow. And I understand you may not see your worth in the world anymore, but you are the one that holds everything together.

Please talk to your family and tell them everything, from your last post if seems like you have good parents. Which is great. They want you to be with them and talk to them (deeply). If you dont think that will help please message me.