Having had the common background we experienced, it creates a bond. We can all 'relate' even though we have perhaps chosen some different paths with different beliefs ideas, as Nina pointed out.
And as Dede mentions, yes, it is a brotherhood and sisterhood. Of course, we're all sisters and brotehrs because we're all human beings, but also we are brought together with other things in common, relating to our feelings about our lives as jws. I think that any time people come together with a commonality of purpose and experience, it can be termed a brotherhood and sisterhood.