I’m not really an official member of any real group come to think of it, because I’m not that active in them (I do a lot of stuff myself, teach, practice, fight, etc.). However I’m almost always welcomed in to any group who have seen me or knows me in some way, so I guess I’m kind of a member in every group I meet.
The group I run I guess would be the best thing I could say, it is a subdivision for a high school club (which a friend and teacher runs) that is a living history group in my area.