Workaround for cutting in nested family by family with void.

[choshQT24J]

I have a nested family file.
I need to cut a child-family by another child-family with only void in it.
By Revit api, this is only able to do in project not family edit.
However, I need to do this in family.
So, I start to find a workaround.

The way I think is like this:

1. Get the familyInstance of the cut family. (No prob)

2. Get the GenericForm of it （it is void inside only）※Still trying here

3. Copy the genericform into outside of that family. 

4. delete the familyInstance.

5. cut by that copied familyInstance.

However, everything is not going well, any suggestions or other ways please.

[choshQT24J]

Any ideas, please.

I have tried these two things. 

1. Edit the family of the child-family and copy the genericForm inside of it into the parent-family. However, the parameter and the location are all gone. 

2. Copy the geometryObject of the familyInstance and create it as a directShape. It perfectly clones the shape but not able to cut.