My twin sister doesn't have SA so as close as we are she doesn't really understand. We work together but live very separate lives. I will admit to using her as a crutch when I need to go places. I'm glad you have your sister to help you out.I am a twin, my sister does have social anxiety, too. We help each other out a lot and it's nice to know that there's someone who knows exactly how I feel.
I don't know whether we "inherited" SA or we developed (or worsened) it because we simply did not "need" to socialise. As kids we've always been together and so there simply was no need of making new friends and develop social skills.
Story of my life Not only is my twin sister completely normal but so are my other siblings. They are all outgoing and have no major issues that I know of.xD I know how random this must sound but this thread makes me imagine Siamese twins, one of whom has normal social skills and the other having severe social anxiety. Just imagine the conflicts they'd have.