SCA members consider each other all to be 'cousins,' part of the vast extended family that makes up the group at large.
-- Mistress Arlys o Gordon
Also, often heard used by the royalty (or other nobility) to refer to their equals in other kingdoms/principalities/baronies. For example, the baron of Wyewood might refer to "their cousins in Aquaterra", meaning the Baron and Baroness of Aquaterra.