When Kids Are Cruel to their Siblings

A reader asks for advice.

I haven’t answered a subscriber question here in a while, so I thought I’d answer this excellent one, which I’m sure a number of you can relate to:

My daughter, 7, HATES her brother, 4.5. I don’t mean like they fight over toys or she gets mad if he gets more than her — I mean actually hate. She’ll randomly kick him on the couch just sitting there, or push him, pull his hair — anything to just be in his bubble unwanted and make him scream. Zero encouragement, just put-downs when he’s learning something, like a typical “mean girl” would do. But it’s all the time and almost like some dark force comes on to her and she has no idea what happened. It’s freaky! Life is so different when he’s not around and vice versa and it really bums me out. Consequences or getting mad does nothing, she forgets within a minute. Any suggestions?

My first thought is: This sounds really hard! I am sending hugs across the internet. It’s painful when kids act out in ways that we don’t understand. And it’s especially hard when one child is hurting the other.

I can’t say for sure, but this could be an example not of sibling rivalry or sibling fighting, but of sibling bullying. We need more studies on sibling bullying than we have, but the existing research suggests that it’s common — that between 10 and 40 percent of kids with siblings are bullied by one at some point. Most sibling fighting is not bullying, but it crosses over into bullying when the following criteria are met: