You are NOT inferior at all. The brother in law and various family members are taking advantage of you and your non-confrontational ways. (I am the same way and so is my husband.) I don't know what the circumstances are but I would say to tell your brother in law to mind his own business and quit talking to him. If its too hard to say to his face (which I completely understand), write him a letter or an email. Tell him the stuff you told us: you are an adult with grown children, married, and take care of yourself, you don't need nor WANT him butting in and changing things you have decided. I, personally, would tell him that he doesn't need to be a part of my life unless he understands he has no right to bully me around or try to control ANYTHING about me. You are not whining, by the way, you are hurt and upset, that's totally OK! Your brother in law is the jerk here.
ARG! Why are some people soooooo mean!?!?
And I am sure you are smart. Look at this like an assignment at school...you have to figure a way to get him off your back and out of your business. You have ?? days to do it. What are you going to do?