I wrote:
"The OP is not worrying about them. He's worrying about himself."
You wrote:
"Incorrect. I'm worrying about them as I feel obligated to help them in some way as people generally do with family members"
However, previously you wrote:
"I'm posting here not to vent but because I really am puzzled by the whole thing. I don't understand why I'm so different from everyone else in the family."
Two things:
First, no where in that original post did you say you want to find a way to help them, but you don't know how. It was all about how different you were, and dismissing any advice, but it was so bad.
Second, no where do you suggest your family wants help. Maybe they are happy with their lot. Some times you just need to accept people as they are. You can offer help or talk about alternatives, but it is up to them to grab it.
Truthfully, you will be better off if you just accept the fact. They are who they are. Accept it, and accept them. If you tell your brother to be quite when he is spouting off he is going to react. Just let him spout and realize that's about him. It's nothing to you. So don't make it about you, and it will die out. If your sister is fat, it's her choice. You don't need to help her unless she asks.