Subject vs. Object Pronoun

I came across the following sentence in a Cambridge ESL book: "One difference between my parents and me is that we don't have the same eating habits".

I was wondering why the object pronoun me is used instead of the subject pronoun I ?

I know that the the SP is used when the person is the doer of the action (I ate the cake.) and the OP is used when the person is the receiver of the action (He hit me) but in the above case it doesn't seem so clear.

Thanks kindly.