I don't have FTM for the Max, but maybe you can see the idea here and apply it to the Mac
Identify the top-of-line ancestors you have in common
File > Export
Choose Each top-of-line ancestor, then DESCENDANTS (this will include spouses)
Repeat for each top-of-line ancestor you have for that person.
Do you want to restrict data for people born after a certain date. For example, I have used:
Vital Fact > Birth > Is After 12/31/1929 (or you could use 1919, 1920, etc.)
You may have a check box to privatize, but I don't use it. Privatizing within the Windows Version of FTM is set for 120 years (ie today would exclude all born after 02/27/1893) - which deletes too many for me..
Choose > Gedcom 5.5
More choices await re including all spouses, media, private facts, etc, etc,
Choose your destination, etc...
Note that actual media do not export via Gedcom - Gedcom is a text only file.
If you have a lot of peripheral relatives, and you want to share them (ie mulitiple spouses, step-children, families of spouses, etc) you may want to choose an ancestor of this person and run an Extended Family Chart
Detach whoever you decide to be your selected person from the rest of your database.
UNCHECK Include Everybody in this file
Right click in blank area of report, Slect All
Right click in blank area of report, Export.
I hope you can interpolate the above options to the Mac.