Identify a consequence for any child who hits or bothers the other, such as having to run around the house or up and down the stairs 3-5 times in order to help diminish the excess evergy available to be a nuisance to his/her sibling. Then, whatever consequence is given to the one doing the hitting or bothering, the same consequence is given to the one who tattles. This will rapidly you function as a referee, which you cannot justly and fairly do anyway.