Swordy Quest clans

Hi,
does anyone know how to add people to your clan in Swordy Quest?
As I remember it, from playing a long time ago, you just have to have them as friends in Game Center, and as long as they're playing SQ it should just work, right?
But now, coming back to the game, I find that my clan size is back to one, but I still have said friends from a few years ago, and I'm sure some of them still play the game.
So, anyone know how I can fix it? Or has the process changed?