There is no polite way that I know of to tell someone to stop interfering.
A: We are family.(If it is just you then change "we" to "I".)
B: No, we are not. And I don't appreciate you sticking your nose in my business. It is none of your business, for one thing, how many bars of soap we have in the bathroom or even whether we have soap. We deserve to have some privacy.
Student or Learner