You don't consider the right hand to be the lead hand when it comes to playing a keyboard?

This is relevant, especially when first learning to play guitar, I think. I'm right- handed. But I have a feeling I wouldn't likely be able to play rhythm as well with my left hand. (And, edit- I guess Esn made that point ahead of me). Though I think I roll a coin better with my left hand than right, and I swing a bat left-handed. And yo, I'm a fraternal twin and my sister and I are both right-handed, so there. .

Thinking further about the left-handed batting, my left arm always felt like it was in the way when I tried to swing right-handed. And in swinging left-handed, I think maybe the pull of the right hand leads and does most of the work so,

Wikipedia knows everything:

http://en.wikipedia.org/wiki/Handedness#Genetic_factors

Short version: the extent to which genetics influences handedness -- if any -- is complicated.

HAHAHAHAHAHAHAHAHAHAHAHAHA!!!! Hilarious! (unless I am reading into that wrong and in that case I just embarrassed myself)