I'm looking for the adjective that goes with sibling. My sentence would be something like:
The [...] relationship.
So the adjective would be used to denote that the relationship is one between siblings. A native speaker told me it was simply sibling, however, I'm not convinced. I have tried googling for the answer, but it hasn't yielded any results as of yet.
Unfortunately, my Oxford dictionary is having a sleepover at one of my fellow students.