I wonder if there are family tree service on the web which is based on a self-service model. No one can maintain up to date info on family member other than them. So, providing a mechanism to create family tree with each node owned by that person with update permission would be great. Also, a mechanism to create dummy node and send invite to that node person for allowing them to sign-in and take ownership of their node.
Each person should see their node as the center and have upward, downward, and sibling connectivity and should have the ability to navigate and view the public profile. Allow, each node to create a profile (public and private, close relatives only) with photos, links, other data etc.
Interesting twist to family networking (instead of social networking)! Only question is "who wants to keep in touch with relatives", right?!!