Ten Fern
In Demoux's Worldhopping as part of the 17th Shard, has he interacted with the Ghostbloods, and if so, does he know Thaidakar is Kelsier?
Brandon Sanderson
He has interacted with the Ghostbloods. I don't know if he's made that connection or not, I would have to write some stuff in his viewpoint and see where it falls in the timeline. He knows Iyatil and her brother and where they came from, that's a group from where Demoux currently makes his base of operations.