Rebecca, have you thought about talking all of these family dynamics over with a counselor? I found a lot of relief in that... Life got exponentially better when I no longer cared who got what, who favored who, who thought what about me, or anything else. When I could focus all of my energies on ME and the people who treated me well, and the rest could just go stew in their own juices.
Nowadays, my family's opinions, and their gossip, and their favoritism, and everything else, is like white laundry flapping on a clothesline far away...I can barely hear it, it doesn't affect my choices, and it has NO power to ruin my day.
That's what counseling did for me...maybe it could help you too?