You might say : 'Where do you come in the pecking order ...?' if you want to ask what the person's 'position' in her family is, hierarchy-wise, compared with her sisters.

"pecking order" refers to hierarchy status, so your asking 'What's your hierarchy status among your sisters in the family?' There's nothing wrong with the sentence exactly but It's a bit ambiguous. I'm not sure in what situation anyone would ask this question.