What are your sibling pet peeves?

Here's mine. My sister and I shared a bathroom growing up. When I was using it in the morning, she'd often come in without warning and grab shit (..not literally). I'd tell her to at least have the decency to knock, since fifty percent of the time I'd be sitting on the bowl. Over the years there's been improvement, but today it happened again. She knocked and said "Can I come in for a sec?" I tell her to wait a minute. Three seconds later, guess who barges in? You're twenty, sis. Learn some bathroom etiquette.