So you have a family let's say a "Toilet". This toilet is working great in your project you can schedule all the parameters that belong too it, but one thing is missing. The "Flush Handle" of the toilet just wont schedule any of the parameters why is that?
Well if this is you then we have the solution, certain families at times you might want to have nested into another. Example would be two separate families the "Toilet" and the "Flush Handle". The Flush Handle is nested into the Toilet family so they load together in my Revit project.
However in order to have a nested family schedule you need to open the nested family "Flush Handle" select Family Categories and Parameters and make sure Shared is checked in the dialog box under Family Parameters (see photo)
hope this helps Enjoy!