I have DD 11 and DS 13, so far we've had:
DS sneezes too loud.
DD doesn't flush the loo.
DD leaves sweet wrappers on DS side of the back seat of the car.
DS went into DD room without asking (I await the return of this as it's inevitable. We actually have a camera in DS room in case he has a fit in his sleep so she can't deny it).
Waiting for "that's my present not yours" and "he/she ate more than his/her share".