I would like to get a clone of geni.com. You can use an open source social networking software (for example Elgg - [url removed, login to view]) as a platform for creating the site.
Majority of the functionalities of [url removed, login to view] are already included in a typical open source social networking software, you just need to add these functions, which are not present in Elgg (or any other platform, which you prefer to use). You could also use functionality from PHP Ged View ([url removed, login to view])
In addition to current features (which you can see at [url removed, login to view]), a language-module is needed - it must be possible to add additional languages and to edit all texts of the site (available in GedView).
You can choose yourself, which software you want to use as platform for the site, however interface, functionality and outlook must be similar to Geni. Please do take a good look at Geni to understand functionality of the site.