So this has come up a bunch in the last few weeks so I thought it was worth mentioning.  If you need to take a get a family from a model that you have linked in copy paste and Tab is the trick.  You can use the “TAB” key to select elements through a linked model, this will allow you to see all the properties of that element or copy it to the clipboard.  Then you can use one of the paste options to put it into your project.