To be thrown out of your room for your roommate to have sex with a blood relative. esp. if blood relation is specifically stated or implied in the eviction.
Roommate 1: "Hey man, can you be out from 3 to five? My cousin is coming to visit and I want some time to put the moves on her. You know?"
Roommate 2: "Dude, not cool. You can't insestile me without at least 24 hours notice."