Hm, I would call it "graded ingroup loyalty", to quote an Arab saying "me and by brother against my cousin, me and my cousin against the world". Instead of a binary ingroup and outgroup, other people are gradually more or less your ingroup, spouse more than cousin, cousin more than buddy, buddy more than compatriot, compatriot more than someone really far away.
But note that reciprocity is almost the opposite of loyalty. That kind of tribalism is dysfunctional in the modern world, because:
Rather than a static loyalty, it is more interesting to ask how people move into and out of your ingroup? What elicits our feelings of sympathy for some more than others? What kind of institutions encourage us to sympathise with other people and stand in their shoes? What triggers our moral ...
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.