Thank you for your reply, OnceUponACat. It does sound like there is much that is similar between your brother and my son. A hut in the woods is a very perfect symbol of the place where my son was mentally. I'm sorry that things are so hard for your brother.
When you said that your brother hates you, my instant reaction was to say 'No he doesn't!'. I know that is daft, because I have no knowledge of your relationship with him at all. But there were two things in my son that looked like hostility and in fact weren't hostile at all.
One was his behaviour as a child to his younger brother (who is very very different from DS1 as you are from your brother and finds it easy to be happy and connected). As a child my son picked on his brother endlessly and aggressively and it was a source of many confrontations between DS1 and me, which I regret immensely. I now understand all this unpleasant behaviour as a very muddled and inept attempt to reach out to his younger brother and feel connected to him. In later life DS1 made lots of conscious efforts to interact with his brother positively. He never seemed to feel confident about how to do it, but the will was there and I think he loved his brother.
The other thing that looked like hostility was his very 'masked' emotional appearance. In some way that I don't understand it was hard for him to express feelings in his face and voice and manner. It looked aloof, even aggressive and intimidating, but I know for a cast iron fact that behind the exterior was kindness and gentleness and confusion.
I don't think he resented his brother for 'having it easy' in respect of finding happiness and satisfaction and connectedness. He just felt confused by how hard it was for he himself.
I'm always reminding my younger son that the experience of having such a troubled brother was hard for him, too, and that he needs to be kind to himself and take care of himself. So I want to say the same to you, OnceUponACat. Be kind to yourself.