I don't know a lot about your relationship with him, but I could speculate. I remember when you first posted you said you loved him, but you cited some additional things like his condition and how you were never in a situation like that, but you wanted to be a good person and look after him with extra care due to his condition. I suppose this inner drive remains unfulfiled. You won't be able to know what it's like to give all you've got and love someone regardless of their health condition. However, the real reason why you won't be able to do that is not due to any personal fault, but due to the fact that he wasn't up to taking initiative and making his life better, rather using his condition as a crutch to get sympathy out of people. You're also doing it to keep peace in your family, even though you feel that some of them were unjust in their treatment of him, you still value your family harmony. A part of you may feel that you were unjust to him because of that, but in reality that's not the case at all and with time you will see this more clearly.
Once again just a speculation, I'm sure there's a lot that I don't know.