When a member of the opposite sex (or same sex) declares you to be "brother/sister", thereby ruining all potential chances of sex.
Guy: Would you like to go out with me?
Girl: I'm sorry, but you're like a brother to me.

Sibling-zoned!
by LanaDangerZone April 1, 2012
Get the Sibling-zoned mug.
Pretty much the Brother Zone and Sister Zone mashed into one convienient term.
Jen told me she liked me like a brother. How the fuck do you get out of the Sibling Zone?
by Mofos in the Zone November 5, 2009
Get the Sibling Zone mug.