Originally Posted by Kriston
As I have always heard it, siblings are usually within 10 IQ points of one another, barring some brain injury. That's the number I always hear thrown around. I have no source to cite though.

Anyone know where that "common knowledge" comes from?

I've heard the 10 I points thing, too.

My mother's siblings both earned PHDs, but she did not. However, both her siblings listened to her advice.