The Christmas when all the ornaments fell off the tree because of "the dog?" The time the neighborhood kids "accidentally" rollerbladed through the shed? So, when a Reddit user asked, "What secret have you and your sibling managed to keep from your parents?" people were ready to share the sacred contract they have with a brother or sister that they'll never reveal.
When we were in middle/high school, my younger brother used to get in trouble at school a lot. Whenever the school called our house to to inform my parents, I would answer the phone and pretend to be my dad. - sidestreetdrew
I don’t think they know about the time we got into the unwrapped Christmas present stash and looked at all our presents (about a week before Christmas). They never said anything about it, at least. But I felt really guilty about it, especially when it came time to unwrap and I had to fake surprise. Never wanted to get into the Christmas stash again after that.