From my best guess, and I did really look, there appears to be no way to link together characters and make a family tree under the new system.
Open the article editor. Look really hard. Realize it's not there. Cry.
That is true, relations and family trees are still accessible only by the old interface. This is not a bug, it is part of the migration process. :)
I will wait with anticipation then. Sorry, I didn't know.