That being my line, I already know all about the Bachs. However, I thought you'd be at least somewhat interested in hearing the personal observations of a jaded old unspectacular working stiff musician who has been around the Bach, er, Bloch, a few times, rather than pointing to a noteworthy famous example we've all heard of.
If Grandpa was a virtuoso violinist, you're much likelier to get those crucial violin lessons before age five, when the muscles and bones of the fingers are most malleable and the neural pathways are most easily canalized, than if through mischance you find yourself growing up in a family of electrical engineers with no institutional memory of your violinist grandfather.
Ditto my previous comments. I grew up around all four of my grandparents, who all told us kids about life in their respective families while growing up. As it happens, even today, my "engineer father" is still the self-appointed proud family historian, and has made it his hobby and passion to draw up detailed genealogies and histories going back at least 5 generations. If anyone would know of any "virtuoso anybody anything" in the family tree, he would. There just aren't any. Yet despite the mutation, I got to be pretty decent; good enough to make a living. ;)
Well, likewise, I know something about this from personal experience, too. Check out http://www.pulpless.com/jneil/memoriam.html on my website.