I've only mentioned it once before, but I'm working on exporting FOAF from Gedcom. I hadn't touched it in a while, but I've recently revisited it.
The current implementation "works" (e.g. HTML View, FOAF View), however it fails to split things up along family unit lines (i.e. what children are associated with which spouse and which family, exactly, was this person a part of as a child).
FAM 1 (C)
FAM 2 (S)
FAM 3 (S)
FAM 4 (S)
FAM 5 (S)
The above example shows that Person X is part of 5 families. 4 as a spouse and one as a child. You can also see, specifically, that Children 1-3 were with Spouse 1 (hence a family unit).
It's important to note that each person and family unit is given a unique ID.
I was hoping to use foaf:Group to associate each person with their respective families, though I'm not exactly sure how.
You might have noticed that I've omitted any siblings of Person X in the above example. That may cause a problem due to the fact that the foaf:Group in which Person X is a child would be split over multiple files.
If foaf:Group had an inverse (see wiki entry) then i might be able to just say that Person X is a memberOf families 1, 2, 3, 4 and 5 and aggregate those files, focussing on Person X's relationships. Though i don't see a way to show relationships between people in groups.