Question: Is there a scientific reason for us hating our siblings?

Sam Carr answered on 12 Jun 2017:

Well, sibling rivalry is though to be something that occurs in many, many species. In animals and birds it’s because, scientists have suggested, the little ones (the young) are sort of competing for a fixed amount of resources (which could be food or something else). The parents only have so much to offer so there can be a bit of infighting about who gets what.

It’s more complicated because in other species it’s thought that the parents sort of try to “judge” which of the little ones is in most need of the resources and then offer more to that little one – to even things up. But – in reality – the parents often mess that up and make mistakes. They incorrectly judge who needs what, who needs more, and who needs less – and that can be costly!

In humans it’s thought that the “resources” we’re competing for with our siblings are much more complex than food alone. In some senses, we’re competing for love, attention, recognition, support. Siblings (who frequently DO “love” each other) can quite literally be competing for these things – and that can cause quite a lot of powerful and complicated feelings to arise!

And then let’s not forget that parents can “create” sibling rivalry by treating siblings differently and in ways that the children themselves experience to be really unfair.