Children will sometimes use the threat of parental consequences to manipulate or blackmail their siblings into letting them have their way. One way that this sort of thing plays out is when one child develops the pattern of "tattling" on others, calling parents attention to wrongdoings the other child may or may not have done so as to get that child into trouble and look good in comparison. Though parents may appreciate knowing about actual misdeeds of their other children (so that those misdeeds can be corrected), it is not a good idea to reinforce such tattling behavior, as even in the best case scenario, it tends to break down any basis for siblings to trust one another. Parents may want to explicitly label tattling behavior as something undesirable, and set consequences on that behavior so as to discourage it from reoccurring.
Should parents notice that one of their children continuously picks on or exerts power over another, the situation should be treated as a bullying scenario, as described in the next.
A children's mental health professional should be consulted if sibling bullying behavior does not stop despite parental intervention, or if other forms of sibling rivalry or competition cannot be brought under reasonable control and end up causing emotional or behavioral problems such as sadness, social-withdrawal, anger outbursts at home or school, avoidance of school work or homework, or other peer-related problems.