I just read this thread but I am curious to know more about your sister. It seems she is being cheated on as well. Either as an EA or a PA. It sounds like your sister doesn't believe you? I almost think explaining what is happening to your parents is needed. Surely they wouldn't want to invite two people to a Thanksgiving gathering that are both cheating on their own flesh and blood? But if you haven't had a honest conversation with your sister maybe that is step 1.
