I am the eldest among my siblings with my brother being the middle seems to fit a sociological model examined by Dr. Kevin Leman, author of the Birth Order Book.

Middle children are sometimes diverse in that they are "guaranteed to be opposite of their older sibling" and often have the feeling that they are ignored in favor of their older and younger siblings. They are also described as having personalities that lean towards being secretive and can often serve as peacemakers between their older and younger siblings. ~ wiki.

!LADY