Definitely. Though a certain amount of bickering between siblings is normal, too much can foster resentment, anxiety, and low self-esteem in both kids. First, ask yourself why this may be happening. One possibility is that your older kid feels the family rules are unfair. Before you confront her, evaluate your own behavior: Do you give more support and nurturing to your younger child? Do you compare your kids a lot? Are family rules applied fairly to both? Correcting these imbalances usually leads to less rivalry. You should also talk to your daughter about what's going on, and be sure to set limits on teasing. A good rule: It's okay to tease, but not about shortcomings. And if your kid continues to break the rule, she should be punished appropriately -- with an earlier bedtime or losing her computer privileges for a couple of days -- to remind her that it's not okay to hurt people's feelings.