Voids in Families

When you are creating Revit Families, if you need to add a void to the Family to cut elements that are modeled in the Family, it is easier to create the form first as a solid element and then in its properties change it to a void. If you create a void straight away it will try and cut all of the existing elements in the family. 

This way you can select the objects that you want the void to cut (using the Cut tool, in the modify ribbon). You are in control!!!