A brother that is a big brother (i.e. has younger siblings) and is also a little brother (i.e. has older siblings) is a medium brother. First formulated by a 6 year old boy named Gordon S. from Surrey, B.C. Canada; who happens to be a medium brother.
"That's my big brother Perry, and my little brother's Dylan and Jayden -- I'm a medium brother."
by Gordon S January 20, 2013