A little digging reveals they are the "Tuttle Kids," raised by a very accomplished musician, Jack Tuttle, who is no doubt being bombarded with requests for music lessons at the moment. His site is worth checking out if only to read some of his favorite responses he has received from the video's posting on YouTube.
I was amazed to see what has been added to his website just since yesterday. The video is obviously changing their lives dramatically. I hope their 15 minutes continues to follow them throughout adulthood.
The local NBC affiliate in San Francisco ran a feature on them:
http://www.youtube.com/watch?v=g9zBzHXVL0whttp://www.jacktuttle.com