I read in a previous thread about twins, one of whom was identified by testing for a gifted program and the other who missed the cut off, that siblings are usually within 5 points on each other in IQ. The source for this comment was Linda Silverman at the Gifted Development Center.
My DS is HG and 2E and DD is PG. They obviously have a slightly larger gap in IQ than 5 points but not by much. DS' strongest score was PRI and DD was VCI, so they are totally different kids even though pretty equally intelligent. DD, however, is not 2E.
As to the 2E, some LDs run in families. like ADHD or dyslexia. DS is ADHD/dysgraphic. I strongly suspect DH is undiagnosed ADHD but neither of us is dysgraphic. My older brother IS both ADHD and dysgraphic and DS is very like him in many ways.
There seems to be a pretty strong genetic component for IQ and 2E (at least to some LDs) but everyone's genes have recessive traits that may not show up in you but may show up in your siblings or your kids!
