That's too bad about your brother. As for your sister, that sux.
My family has pretty much written me off as well. I used to be sad about it, but eventually I just decided not to care anymore and live my life without them. At first I thought I'd send out death certificates to certain members of the family -- not one with my name in, oh no, but with their name. Just to do the same they did to me, basically. But then, I figured that it would be a waste of time and energy. If they don't want to be part of my life and if they can just write me off because of who I am, then I don't need those type of people in my life, family or not. I have a lot of friends who accept me for who I am and they have been more family to me than my family ever has.