First of all its not Rivet, its Revit. (Sorry, I'm not trying to be a grammar nazi but a lot of people get this wrong).
Secondly, yes you can import 2D or 3D DWG drawing data into a family. However, this is highly discouraged. In fact, at my company, it is not allowed at all. The only application that needs to be used in creating a Revit Family is Revit - period.
Hope this helps.