|Hi Scott I use this a lot but do not know if it will HELP Have a play with it.|
I would suggest to find the oldest/earliest Member of one of the ones you are talking about, and see if by using HIM/HER
as commencement whether this then selects all of that FAMILY which you can then use as a separate GEDCOM. If so you should be able to do this on other parts of your ORIGINAL GEDCOM.
Hopefully that I am correct.
Please let me know
All the best