You won't miss what they have become but you may remember missing how things once were ....and that may not be that great of a memory either
I don't think she's expecting anything other than a thank you. People let family off too easily, and wouldn't allow people other than family to treat them so poorly. Unless you are related to someone like her brother, you won't understand.
Your brother is jealous. You have what he wants, stability. So instead of being proud of you for making a good life for yourself and not ending up like him (on drugs,drunk, and broke) he resents you. My sister is the same way and no matter how nice I am to her and her kids, they talk behind my back and treat me terrible. I wish I could walk away and start life somewhere else but I can't. Take care and forget about being the good sister, it will only hurt you in the long run.
Save yourself, move on. Find joy elsewhere. When someone shows you they're true colours, believe it.
AWESOME!!! Could not have summed it up any better.