Yes but that does you very little good when you need to provide remote tech support to your parents. VNC doesn't help you forward ports through router firewalls or provide dyndns so you can actually find the IP address of the computer you installed it on.

If you have a forward on your firewall, you can tell the remote party "right-click on the VNC icon in the lower right, add new client, and punch in $MY_IP_ADDRESS" Their VNC service will connect to your VNC viewer.

You can also script it - I have a Cygwin service that I made that checks a website for a command to trigger a reverse VNC connection.

Doesn't work when your family is behind double NAT.

Why wouldn't it? It only relies on the ability to create a single outbound TCP connection; surely double NAT doesn't impede that?

If both parties are double NAT, then sure, you have a problem, but aside from that; as long the party you are connecting to doesn't -- it should work fine as described.