There wouldn’t be any easy way to tie these two field groups together.
Normally, when setting up a flex field the layout name would be something like ‘full_width’, ‘two_columns’ etc. and then each layout would have the fields used in that layout.
There is not a way of selecting which of the layouts set up in another field group to use in each of the layouts of the second groups without an overly complex amount of javascript because there would be no way for the second group to be “aware” of what was created in the first group.
